mb/google/mistral: Move selects from Kconfig.name to Kconfig

Selects should be done in the Kconfig file instead of Kconfig.name and
not mixed over both files.

Change-Id: I1033a974a818308b31e1334cad5869d2cd81bd9e
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/75017
Reviewed-by: Martin L Roth <gaumless@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/mistral/Kconfig

@@ -2,6 +2,9 @@
 config BOARD_GOOGLE_MISTRAL_COMMON  # Umbrella option to be selected by variants
 	def_bool n
 
+config BOARD_GOOGLE_MISTRAL
+	select BOARD_GOOGLE_MISTRAL_COMMON
+
 if BOARD_GOOGLE_MISTRAL_COMMON
 
 config BOARD_SPECIFIC_OPTIONS

src/mainboard/google/mistral/Kconfig.name

@@ -2,4 +2,3 @@ comment "Mistral"
 
 config BOARD_GOOGLE_MISTRAL
 	bool "->  Mistral"
-	select BOARD_GOOGLE_MISTRAL_COMMON