initramfs: specify $(src)/gen_initramfs.sh as a prerequisite in Makefile

Specify the dependency directly in the Makefile.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Greg Thelen <gthelen@google.com>

usr/gen_initramfs.sh

@@ -235,7 +235,7 @@ arg="$1"
 case "$arg" in
 	"-l")	# files included in initramfs - used by kbuild
 		dep_list="list_"
-		echo "deps_initramfs := $0 \\"
+		echo "deps_initramfs := \\"
 		shift
 		;;
 	"-o")	# generate compressed cpio image named $1