mb/google/rex: Create a `rex` model for easier variant integration

This patch creates  a rex model so that other variants developed using
`rex` baseboard are easy to land without duplicating the config
selection.

So far, `rex0` and `rex_ec_ish` are developed using the `rex` model.
The plan is to extend the support for `rex4es` and `rex4es_ec_ish`
variants.

TEST=Able to build and boot google/rex.

Change-Id: Id4e8d1162da93b7266ee1108f870e89b6d884ab9
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/76608
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Reviewed-by: Jakub Czapiga <jacz@semihalf.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kapil Porwal <kapilporwal@google.com>
diff --git a/src/mainboard/google/rex/Kconfig b/src/mainboard/google/rex/Kconfig
index 014c3a7..9c75508 100644
--- a/src/mainboard/google/rex/Kconfig
+++ b/src/mainboard/google/rex/Kconfig
@@ -44,6 +44,16 @@
 	select SYSTEM_TYPE_LAPTOP
 	select TPM_GOOGLE_TI50
 
+config BOARD_GOOGLE_MODEL_REX
+	def_bool n
+	select BOARD_GOOGLE_BASEBOARD_REX
+	select DRIVERS_GENERIC_MAX98357A
+	select DRIVERS_GENESYSLOGIC_GL9755
+	select DRIVERS_INTEL_ISH
+	select DRIVERS_INTEL_SOUNDWIRE
+	select DRIVERS_SOUNDWIRE_CS42L42
+	select DRIVERS_SOUNDWIRE_MAX98363
+
 config BOARD_GOOGLE_BASEBOARD_OVIS
 	def_bool n
 	select BOARD_GOOGLE_REX_COMMON
diff --git a/src/mainboard/google/rex/Kconfig.name b/src/mainboard/google/rex/Kconfig.name
index 8084a04..94ae1a0 100644
--- a/src/mainboard/google/rex/Kconfig.name
+++ b/src/mainboard/google/rex/Kconfig.name
@@ -2,13 +2,7 @@
 
 config BOARD_GOOGLE_REX0
 	bool "-> Rex 0"
-	select BOARD_GOOGLE_BASEBOARD_REX
-	select DRIVERS_GENERIC_MAX98357A
-	select DRIVERS_GENESYSLOGIC_GL9755
-	select DRIVERS_INTEL_ISH
-	select DRIVERS_INTEL_SOUNDWIRE
-	select DRIVERS_SOUNDWIRE_CS42L42
-	select DRIVERS_SOUNDWIRE_MAX98363
+	select BOARD_GOOGLE_MODEL_REX
 
 config BOARD_GOOGLE_SCREEBO
 	bool "->  Screebo"
@@ -21,13 +15,7 @@
 
 config BOARD_GOOGLE_REX_EC_ISH
 	bool "-> Rex EC ISH"
-	select BOARD_GOOGLE_BASEBOARD_REX
-	select DRIVERS_GENERIC_MAX98357A
-	select DRIVERS_GENESYSLOGIC_GL9755
-	select DRIVERS_INTEL_ISH
-	select DRIVERS_INTEL_SOUNDWIRE
-	select DRIVERS_SOUNDWIRE_CS42L42
-	select DRIVERS_SOUNDWIRE_MAX98363
+	select BOARD_GOOGLE_MODEL_REX
 
 config BOARD_GOOGLE_OVIS
 	bool "-> Ovis"