board/common: Remove unused MMC image creation script

Remnants from the olde country.

board/common/mkmmc.sh

@@ -1,22 +0,0 @@
-#!/bin/sh
-
-set -e
-
-common=$(dirname $(readlink -f "$0"))
-root=$BUILD_DIR/genimage.root
-tmp=$BUILD_DIR/genimage.tmp
-
-
-mkdir -p $root/aux
-cp -f $BINARIES_DIR/uboot-env.bin $root/aux/uboot.env
-cp -f $BINARIES_DIR/rootfs.itbh $root/aux/primary.itbh
-cp -f $BINARIES_DIR/rootfs.itbh $root/aux/secondary.itbh
-
-rm -rf $tmp
-
-genimage \
-    --rootpath $root \
-    --tmppath  $tmp \
-    --inputpath $BINARIES_DIR \
-    --outputpath $BINARIES_DIR \
-    --config $common/genimage.cfg