arch/x86: Clarify help text for 64-bit support

The word "experimental" has been removed from the help text for
HAVE_X86_64_SUPPORT Kconfig. This is because the x86_64 architecture
has now been officially tested and enabled for several x86 SoC
platforms.

This work will provide us with the foundation we need to begin working
with Intel's next-generation SoC platform (which requires to support
64-bit mode of booting by default).

Therefore, we can now remove the word "experimental" from the
"HAVE_X86_64_SUPPORT" Kconfig help text.

TEST=Able to build and boot google/rex64 in 64-bit mode to ChromeOS.

Change-Id: Ibd629f4e2722f3cbabbe297d4481790c9fa9226a
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/83009
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/arch/x86/Kconfig b/src/arch/x86/Kconfig
index 7d25561..c0fe6dc 100644
--- a/src/arch/x86/Kconfig
+++ b/src/arch/x86/Kconfig
@@ -68,9 +68,9 @@
 config HAVE_X86_64_SUPPORT
 	bool
 	help
-	  Enable experimental support to build and run coreboot in 64-bit mode.
-	  When selecting this option for a new platform, it is highly advisable
-	  to provide a config file for Jenkins to build-test the 64-bit option.
+	  Enable support to build and run coreboot in 64-bit mode.
+	  When enabling this option for a new platform, it is recommended to
+	  provide a config file for Jenkins to build-test the 64-bit option.
 
 config USE_X86_64_SUPPORT
 	bool "Run coreboot in long (64-bit) mode"