mb/google/brya: Create mithrax variant

Create the mithrax variant of the brya0 reference board by copying
the template files to a new directory named for the variant.

(Auto-Generated by create_coreboot_variant.sh version 4.5.0).

BUG=b:223091246
BRANCH=None
TEST=util/abuild/abuild -p none -t google/brya -x -a
make sure the build includes GOOGLE_MITHRAX

Signed-off-by: John Su <john_su@compal.corp-partner.google.com>
Change-Id: I7c2fa6a74cc8e37397dea7e67e8cfa6506a49bdb
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63776
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>
diff --git a/src/mainboard/google/brya/Kconfig b/src/mainboard/google/brya/Kconfig
index 5263323..a064ab3 100644
--- a/src/mainboard/google/brya/Kconfig
+++ b/src/mainboard/google/brya/Kconfig
@@ -174,6 +174,7 @@
 	default "Kinox" if BOARD_GOOGLE_KINOX
 	default "Craask" if BOARD_GOOGLE_CRAASK
 	default "Osiris" if BOARD_GOOGLE_OSIRIS
+	default "Mithrax" if BOARD_GOOGLE_MITHRAX
 
 config VARIANT_DIR
 	default "brya0" if BOARD_GOOGLE_BRYA0
@@ -203,6 +204,7 @@
 	default "kinox" if BOARD_GOOGLE_KINOX
 	default "craask" if BOARD_GOOGLE_CRAASK
 	default "osiris" if BOARD_GOOGLE_OSIRIS
+	default "mithrax" if BOARD_GOOGLE_MITHRAX
 
 config VBOOT
 	select VBOOT_EARLY_EC_SYNC