soc/amd/sabrina: Add prompt for AMDFW_CONFIG_FILE

This will allow configuring the concerned config through an external
defconfig file.

BUG=None
TEST=Ensure that AMDFW_CONFIG_FILE is configurable.

Signed-off-by: Karthikeyan Ramasubramanian <kramasub@google.com>
Change-Id: I97817a822c8c41822e699adc31f0e7452f93fdb9
Reviewed-on: https://review.coreboot.org/c/coreboot/+/62971
Reviewed-by: Jon Murphy <jpmurphy@google.com>
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/soc/amd/sabrina/Kconfig b/src/soc/amd/sabrina/Kconfig
index 1be53b5..b393381 100644
--- a/src/soc/amd/sabrina/Kconfig
+++ b/src/soc/amd/sabrina/Kconfig
@@ -344,8 +344,10 @@
 	depends on AMD_FWM_POSITION_INDEX = 5
 
 config AMDFW_CONFIG_FILE
-	string
+	string "AMD PSP Firmware config file"
 	default "src/soc/amd/sabrina/fw.cfg"
+	help
+	  Specify the path/location of AMD PSP Firmware config file.
 
 config PSP_DISABLE_POSTCODES
 	bool "Disable PSP post codes"