base-files: add minimal mmc support

Added minimal mmc support for helper functions:

 - find_mmc_part: Look for a given partition name. Returns the
	coresponding partition path
 - caldata_extract_mmc: Look for a given partition name and then
	extracts the calibration data
 - mmc_get_mac_binary: Returns the mac address from a given partition
	name and offset

Signed-off-by: Davide Fioravanti <pantanastyle@gmail.com>
Signed-off-by: Robert Marko <robimarko@gmail.com>
[replace dd with caldata_dd, moved sysupgrade mmc to orbi]
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>

package/base-files/files/lib/functions.sh

@@ -330,6 +330,19 @@ find_mtd_part() {
 	echo "${INDEX:+$PREFIX$INDEX}"
 }
 
+find_mmc_part() {
+	local DEVNAME PARTNAME
+
+	if grep -q "$1" /proc/mtd; then
+		echo "" && return 0
+	fi
+
+	for DEVNAME in /sys/block/mmcblk*/mmcblk*p*; do
+		PARTNAME="$(grep PARTNAME ${DEVNAME}/uevent | cut -f2 -d'=')"
+		[ "$PARTNAME" = "$1" ] && echo "/dev/$(basename $DEVNAME)" && return 0
+	done
+}
+
 group_add() {
 	local name="$1"
 	local gid="$2"