util/scripts/testsoc: Only select mainboards

The testsoc script was pulling in odd results when the -K option matched
options in sources, Makefiles, and device trees.  Adding another grep to
limit the list to just Kconfig matches ensures that only actual
mainboards are built.

TEST="./util/testsoc -K PICASSO" no longer tries to build mainboard "0"

Signed-off-by: Fred Reitberger <reitbergerfred@gmail.com>
Change-Id: I3860df4520a5594fb9c1a06e75487520b7d5d275
Reviewed-on: https://review.coreboot.org/c/coreboot/+/72655
Reviewed-by: Martin Roth <martin.roth@amd.corp-partner.google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

util/scripts/testsoc

@@ -81,7 +81,7 @@ get_args() {
 			;;
 		-K | --kconfig)
 			shift
-			mblist=$(grep -r "$1" src/mainboard | sed 's|src/mainboard/||;s|/Kconfig.*||')
+			mblist=$(grep -r "$1" src/mainboard | grep Kconfig | sed 's|src/mainboard/||;s|/Kconfig.*||')
 			printf "Adding mainboard for %s\n%s\n" "$1" "${mblist}"
 			echo
 			mapfile -t mainboards <<<"$mblist"