cpu/x86/Kconfig: Mark 64bit support as stable

With SMM holding page tables itself, we can consider SMM support stable
and safe enough for general use.

Also update the respective documentation.

Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Change-Id: Ifcf0a1a5097a2d7c064bb709ec0b09ebee13a47d
Reviewed-on: https://review.coreboot.org/c/coreboot/+/80338
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@gmail.com>
diff --git a/configs/config.emulation_qemu_x86_i440fx_x86_64 b/configs/config.emulation_qemu_x86_i440fx_x86_64
index 7123646..2f6bf78 100644
--- a/configs/config.emulation_qemu_x86_i440fx_x86_64
+++ b/configs/config.emulation_qemu_x86_i440fx_x86_64
@@ -1,3 +1,3 @@
 CONFIG_VENDOR_EMULATION=y
 CONFIG_BOARD_EMULATION_QEMU_X86_I440FX=y
-CONFIG_USE_EXP_X86_64_SUPPORT=y
+CONFIG_USE_X86_64_SUPPORT=y
diff --git a/configs/config.foxconn_g41m b/configs/config.foxconn_g41m
index f5deea5..acb0768 100644
--- a/configs/config.foxconn_g41m
+++ b/configs/config.foxconn_g41m
@@ -1,3 +1,3 @@
 CONFIG_VENDOR_FOXCONN=y
 CONFIG_BOARD_FOXCONN_G41M=y
-CONFIG_USE_EXP_X86_64_SUPPORT=y
+CONFIG_USE_X86_64_SUPPORT=y
diff --git a/configs/config.google_vilboz.x86_64 b/configs/config.google_vilboz.x86_64
index 74036ae..ddb2eda 100644
--- a/configs/config.google_vilboz.x86_64
+++ b/configs/config.google_vilboz.x86_64
@@ -1,3 +1,3 @@
 CONFIG_VENDOR_GOOGLE=y
 CONFIG_BOARD_GOOGLE_VILBOZ=y
-CONFIG_USE_EXP_X86_64_SUPPORT=y
+CONFIG_USE_X86_64_SUPPORT=y
diff --git a/configs/config.hp_compaq_8200_elite_sff_pc.x86_64 b/configs/config.hp_compaq_8200_elite_sff_pc.x86_64
index 9bb5e38..d15f162 100644
--- a/configs/config.hp_compaq_8200_elite_sff_pc.x86_64
+++ b/configs/config.hp_compaq_8200_elite_sff_pc.x86_64
@@ -1,3 +1,3 @@
 CONFIG_VENDOR_HP=y
 CONFIG_BOARD_HP_COMPAQ_8200_ELITE_SFF_PC=y
-CONFIG_USE_EXP_X86_64_SUPPORT=y
+CONFIG_USE_X86_64_SUPPORT=y
diff --git a/configs/config.lenovo_t400_vboot_and_debug b/configs/config.lenovo_t400_vboot_and_debug
index f79d773..6738e43 100644
--- a/configs/config.lenovo_t400_vboot_and_debug
+++ b/configs/config.lenovo_t400_vboot_and_debug
@@ -12,5 +12,5 @@
 CONFIG_DEBUG_ADA_CODE=y
 CONFIG_H8_FN_KEY_AS_VBOOT_RECOVERY_SW=y
 CONFIG_VBOOT=y
-CONFIG_USE_EXP_X86_64_SUPPORT=y
+CONFIG_USE_X86_64_SUPPORT=y
 CONFIG_ARCH_X86_64_PGTBL_LOC=0xfffe8000
diff --git a/configs/config.lenovo_x201_all_debug_option_table_bt_on_wifi b/configs/config.lenovo_x201_all_debug_option_table_bt_on_wifi
index 63becd7..148c77d 100644
--- a/configs/config.lenovo_x201_all_debug_option_table_bt_on_wifi
+++ b/configs/config.lenovo_x201_all_debug_option_table_bt_on_wifi
@@ -10,4 +10,4 @@
 CONFIG_DEBUG_SPI_FLASH=y
 CONFIG_DEBUG_BOOT_STATE=y
 CONFIG_DEBUG_ADA_CODE=y
-CONFIG_USE_EXP_X86_64_SUPPORT=y
+CONFIG_USE_X86_64_SUPPORT=y
diff --git a/configs/config.prodrive_hermes.x86_64 b/configs/config.prodrive_hermes.x86_64
index 506f494..6763aa6 100644
--- a/configs/config.prodrive_hermes.x86_64
+++ b/configs/config.prodrive_hermes.x86_64
@@ -14,4 +14,4 @@
 CONFIG_PCIEXP_SUPPORT_RESIZABLE_BARS=y
 CONFIG_PCIEXP_DEFAULT_MAX_RESIZABLE_BAR_BITS=36
 CONFIG_RUN_FSP_GOP=y
-CONFIG_USE_EXP_X86_64_SUPPORT=y
+CONFIG_USE_X86_64_SUPPORT=y