mb/google/rex: Move BOARD_GOOGLE_BASEBOARD_REX to Kconfig.name

Align project style with other chrome projects.

TEST=built FW not changed

Signed-off-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Change-Id: Icfd1d274216d387cab6feb68afa49fc63c8c52e5
Reviewed-on: https://review.coreboot.org/c/coreboot/+/73761
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Ivy Jian <ivy.jian@quanta.corp-partner.google.com>
Reviewed-by: Kapil Porwal <kapilporwal@google.com>
Reviewed-by: Subrata Banik <subratabanik@google.com>
diff --git a/src/mainboard/google/rex/Kconfig b/src/mainboard/google/rex/Kconfig
index a0eeaea..c716645 100644
--- a/src/mainboard/google/rex/Kconfig
+++ b/src/mainboard/google/rex/Kconfig
@@ -40,9 +40,6 @@
 	select SYSTEM_TYPE_LAPTOP
 	select TPM_GOOGLE_TI50
 
-config BOARD_GOOGLE_REX0
-	select BOARD_GOOGLE_BASEBOARD_REX
-
 if BOARD_GOOGLE_REX_COMMON
 
 config BASEBOARD_DIR
diff --git a/src/mainboard/google/rex/Kconfig.name b/src/mainboard/google/rex/Kconfig.name
index 8216cc9..ca63842 100644
--- a/src/mainboard/google/rex/Kconfig.name
+++ b/src/mainboard/google/rex/Kconfig.name
@@ -2,4 +2,5 @@
 
 config BOARD_GOOGLE_REX0
 	bool "-> Rex 0"
+	select BOARD_GOOGLE_BASEBOARD_REX
 	select DRIVERS_GENESYSLOGIC_GL9755