powerpc/boot: Add lzma support for uImage

This patch allows to generate lzma compressed uImage

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/boot/wrapper

@@ -137,7 +137,7 @@ while [ "$#" -gt 0 ]; do
     -Z)
 	shift
 	[ "$#" -gt 0 ] || usage
-        [ "$1" != "gz" -o "$1" != "xz" -o "$1" != "none" ] || usage
+        [ "$1" != "gz" -o "$1" != "xz" -o "$1" != "lzma" -o "$1" != "none" ] || usage
 
 	compression=".$1"
 	uboot_comp=$1
@@ -374,6 +374,9 @@ if [ -z "$cacheit" -o ! -f "$vmz$compression" -o "$vmz$compression" -ot "$kernel
     .gz)
         gzip -n -f -9 "$vmz.$$"
         ;;
+    .lzma)
+        xz --format=lzma -f -6 "$vmz.$$"
+	;;
     *)
         # drop the compression suffix so the stripped vmlinux is used
         compression=