Kconfig: comply to Linux 5.3's Kconfig language rules

Kconfig became stricter on what it accepts, so accomodate before
updating to a new release.

Change-Id: I92a9e9bf0d557a7532ba533cd7776c48f2488f91
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37156
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
diff --git a/src/mainboard/emulation/qemu-aarch64/Kconfig b/src/mainboard/emulation/qemu-aarch64/Kconfig
index ebdbf16..895446d 100644
--- a/src/mainboard/emulation/qemu-aarch64/Kconfig
+++ b/src/mainboard/emulation/qemu-aarch64/Kconfig
@@ -30,7 +30,7 @@
 
 config MAINBOARD_DIR
 	string
-	default emulation/qemu-aarch64
+	default "emulation/qemu-aarch64"
 
 config MAINBOARD_PART_NUMBER
 	string
diff --git a/src/mainboard/emulation/qemu-armv7/Kconfig b/src/mainboard/emulation/qemu-armv7/Kconfig
index 73b2d5d..181f9a4 100644
--- a/src/mainboard/emulation/qemu-armv7/Kconfig
+++ b/src/mainboard/emulation/qemu-armv7/Kconfig
@@ -39,7 +39,7 @@
 
 config MAINBOARD_DIR
 	string
-	default emulation/qemu-armv7
+	default "emulation/qemu-armv7"
 
 config MAINBOARD_PART_NUMBER
 	string
diff --git a/src/mainboard/emulation/qemu-i440fx/Kconfig b/src/mainboard/emulation/qemu-i440fx/Kconfig
index 8632ef6..3c27b1e 100644
--- a/src/mainboard/emulation/qemu-i440fx/Kconfig
+++ b/src/mainboard/emulation/qemu-i440fx/Kconfig
@@ -42,7 +42,7 @@
 
 config MAINBOARD_DIR
 	string
-	default emulation/qemu-i440fx
+	default "emulation/qemu-i440fx"
 
 config MAINBOARD_PART_NUMBER
 	string
diff --git a/src/mainboard/emulation/qemu-q35/Kconfig b/src/mainboard/emulation/qemu-q35/Kconfig
index 8b97495..3a9bb6f 100644
--- a/src/mainboard/emulation/qemu-q35/Kconfig
+++ b/src/mainboard/emulation/qemu-q35/Kconfig
@@ -41,7 +41,7 @@
 
 config MAINBOARD_DIR
 	string
-	default emulation/qemu-q35
+	default "emulation/qemu-q35"
 
 config MAINBOARD_PART_NUMBER
 	string
diff --git a/src/mainboard/emulation/qemu-riscv/Kconfig b/src/mainboard/emulation/qemu-riscv/Kconfig
index fa6dccc..4d4c900 100644
--- a/src/mainboard/emulation/qemu-riscv/Kconfig
+++ b/src/mainboard/emulation/qemu-riscv/Kconfig
@@ -44,7 +44,7 @@
 
 config MAINBOARD_DIR
 	string
-	default emulation/qemu-riscv
+	default "emulation/qemu-riscv"
 
 config MAINBOARD_PART_NUMBER
 	string
diff --git a/src/mainboard/emulation/spike-riscv/Kconfig b/src/mainboard/emulation/spike-riscv/Kconfig
index 03046f72..2fe0e17 100644
--- a/src/mainboard/emulation/spike-riscv/Kconfig
+++ b/src/mainboard/emulation/spike-riscv/Kconfig
@@ -25,7 +25,7 @@
 
 config MAINBOARD_DIR
 	string
-	default emulation/spike-riscv
+	default "emulation/spike-riscv"
 
 config MAINBOARD_PART_NUMBER
 	string
diff --git a/src/mainboard/emulation/spike-riscv/Kconfig.name b/src/mainboard/emulation/spike-riscv/Kconfig.name
index 17549c6..0c0205d 100644
--- a/src/mainboard/emulation/spike-riscv/Kconfig.name
+++ b/src/mainboard/emulation/spike-riscv/Kconfig.name
@@ -1,3 +1,2 @@
 config BOARD_EMULATION_SPIKE_RISCV
 	bool "SPIKE riscv"
-	help