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-lpc32xx/include/mach/uncompress.h

@@ -55,6 +55,5 @@ static inline void flush(void)
 
 /* NULL functions; we don't presently need them */
 #define arch_decomp_setup()
-#define arch_decomp_wdog()
 
 #endif