mb/amd/padmelon: Use Prairie Falcon configuration

While Merlin Falcon binaries are not available, make it explicit that it's
compiling for Prairie Falcon (it was being surreptitious about it).

Board Padmelon accepts 3 different SOC, just changing some resistors
(soldered or not): Brown Falcon, Prairie Falcon and Merlin Falcon. Code for
Brown Falcon is not currently available.

BUG=None
TEST=Build with prairie falcon.

Change-Id: I1663e4403a32a7d626dd2fa06763f18f4230457e
Signed-off-by: Richard Spiegel <richard.spiegel@silverbackltd.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36824
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Marshall Dawson <marshalldawson3rd@gmail.com>

src/mainboard/amd/padmelon/Kconfig

@@ -18,7 +18,6 @@ if BOARD_AMD_PADMELON
 config BOARD_SPECIFIC_OPTIONS # dummy
 	def_bool y
 	select SOC_AMD_STONEYRIDGE
-	select AMD_APU_MERLINFALCON
 	select AMD_APU_PKG_FP4
 	select BOARD_ROMSIZE_KB_8192
 	select DRIVERS_I2C_GENERIC
@@ -43,6 +42,23 @@ config MAINBOARD_PART_NUMBER
 	string
 	default "Padmelon"
 
+choice PADMELON_SOC
+	prompt "SOC used in padmelon board"
+	default PADMELON_MERLIN_FALCON
+
+config PADMELON_MERLIN_FALCON
+	bool "Merlin Falcon"
+
+config PADMELON_PRAIRIE_FALCON
+	bool "Prairie Falcon"
+
+endchoice
+
+config PADMELON_SOC_IN_USE
+	def_bool y
+	select AMD_APU_MERLINFALCON if PADMELON_MERLIN_FALCON
+	select AMD_APU_PRAIRIEFALCON if PADMELON_PRAIRIE_FALCON
+
 config HAVE_S3_SUPPORT
 	bool
 	default n