powerpc/boot: don't force gzipped uImage

This patch modifies the generation of uImage by handing over
the selected compression type instead of forcing gzip
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/boot/wrapper

@@ -41,6 +41,7 @@ dts=
 cacheit=
 binary=
 compression=.gz
+uboot_comp=gzip
 pie=
 format=
 
@@ -131,6 +132,7 @@ while [ "$#" -gt 0 ]; do
 	;;
     -z)
 	compression=.gz
+	uboot_comp=gzip
 	;;
     -Z)
 	shift
@@ -138,15 +140,21 @@ while [ "$#" -gt 0 ]; do
         [ "$1" != "gz" -o "$1" != "xz" -o "$1" != "none" ] || usage
 
 	compression=".$1"
+	uboot_comp=$1
 
         if [ $compression = ".none" ]; then
                 compression=
+		uboot_comp=none
         fi
+	if [ $uboot_comp = "gz" ]; then
+		uboot_comp=gzip
+	fi
 	;;
     --no-gzip)
         # a "feature" of the the wrapper script is that it can be used outside
         # the kernel tree. So keeping this around for backwards compatibility.
         compression=
+	uboot_comp=none
         ;;
     -?)
 	usage
@@ -369,6 +377,7 @@ if [ -z "$cacheit" -o ! -f "$vmz$compression" -o "$vmz$compression" -ot "$kernel
     *)
         # drop the compression suffix so the stripped vmlinux is used
         compression=
+	uboot_comp=none
 	;;
     esac
 
@@ -412,7 +421,7 @@ membase=`${CROSS}objdump -p "$kernel" | grep -m 1 LOAD | awk '{print $7}'`
 case "$platform" in
 uboot)
     rm -f "$ofile"
-    ${MKIMAGE} -A ppc -O linux -T kernel -C gzip -a $membase -e $membase \
+    ${MKIMAGE} -A ppc -O linux -T kernel -C $uboot_comp -a $membase -e $membase \
 	$uboot_version -d "$vmz" "$ofile"
     if [ -z "$cacheit" ]; then
 	rm -f "$vmz"