ARM: Fix RiscPC decompressor build errors

arch/arm/boot/compressed/decompress.o: In function `do_decompress':
decompress.c:(.text+0x26e8): undefined reference to `error'
decompress.c:(.text+0x2760): undefined reference to `error'
decompress.c:(.text+0x27d8): undefined reference to `error'
decompress.c:(.text+0x2824): undefined reference to `error'
decompress.c:(.text+0x28f0): undefined reference to `error'
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

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

@@ -109,8 +109,6 @@ static inline void flush(void)
 {
 }
 
-static void error(char *x);
-
 /*
  * Setup for decompression
  */