sh: Fix up default zImage target for sh32.

This was using the absolute path, which was confusing the make target.
Switch it to just 'zImage', as per powerpc.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/Makefile b/arch/sh/Makefile
index afe4e63..8da11c0 100644
--- a/arch/sh/Makefile
+++ b/arch/sh/Makefile
@@ -67,7 +67,7 @@
 		   -R .stab -R .stabstr -S
 
 # Give the various platforms the opportunity to set default image types
-defaultimage-$(CONFIG_SUPERH32)	:= arch/sh/boot/zImage
+defaultimage-$(CONFIG_SUPERH32)	:= zImage
 
 # Set some sensible Kbuild defaults
 KBUILD_DEFCONFIG	:= r7780rp_defconfig