ARM: remove unused arch_decomp_wdog()

With ARCH_HAS_DECOMP_WDOG removed from arch/arm/boot/compressed/decompress.c,
all the arch_decomp_wdog() definition at platform level is unneeded.
Remmove it.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Jason Cooper <jason@lakedaemon.net>

arch/arm/mach-ixp4xx/include/mach/uncompress.h

@@ -53,6 +53,4 @@ static __inline__ void __arch_decomp_setup(unsigned long arch_id)
  */
 #define arch_decomp_setup()	__arch_decomp_setup(arch_id)
 
-#define arch_decomp_wdog()
-
 #endif