bmips: split base-files into subtargets

Like done for several targets already, splitting base-files into
subtarget will provide smaller images due to more specific
distribution of files per subtarget and allow to use default cases
more effectively.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/bmips/generic/base-files/etc/uci-defaults/09_fix_crc

@@ -0,0 +1,13 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+. /lib/functions.sh
+
+case "$(board_name)" in
+	comtrend,ar-5315u|\
+	comtrend,ar-5387un|\
+	comtrend,vr-3025u)
+		mtd fixtrx firmware
+		;;
+esac
+
+exit 0