util/chromeos/crosfirmware: ensure $BOARD is lowercase

If $BOARD is not all lowercase, then certain subfunctions of the
script will fail due to case-sensitive comparisons therein. To avoid
this, since all matched strings are fully lowercase, set $BOARD
to lowercase.

TEST: './crosfirmware.sh {akemi/Akemi/AKEMI}' all succeed.

Change-Id: I8ecb613a8d9384e2cccaff5183470e2e9956d0a2
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/82232
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
diff --git a/util/chromeos/crosfirmware.sh b/util/chromeos/crosfirmware.sh
index 3d0f061..e72ff7d 100755
--- a/util/chromeos/crosfirmware.sh
+++ b/util/chromeos/crosfirmware.sh
@@ -137,7 +137,7 @@
 # Main
 #
 
-BOARD=$1
+BOARD=${1,,}
 
 exit_if_dependencies_are_missing