ARM: 9243/1: riscpc: Unbreak the build

This patch fixes the following build error:

In file included from ./include/linux/io.h:13,
                 from ./arch/arm/mach-rpc/include/mach/uncompress.h:9,
                 from arch/arm/boot/compressed/misc.c:31:
./arch/arm/include/asm/io.h:85:22: error: conflicting types for ‘__raw_writeb’
   85 | #define __raw_writeb __raw_writeb
      |                      ^~~~~~~~~~~~
./arch/arm/include/asm/io.h:86:20: note: in expansion of macro ‘__raw_writeb’
   86 | static inline void __raw_writeb(u8 val, volatile void __iomem *addr)
      |                    ^~~~~~~~~~~~
In file included from arch/arm/boot/compressed/misc.c:26:
arch/arm/boot/compressed/misc-ep93xx.h:13:20: note: previous definition of ‘__raw_writeb’ was here
   13 | static inline void __raw_writeb(unsigned char value, unsigned int ptr)
      |                    ^~~~~~~~~~~~

To: Russell King <linux@armlinux.org.uk>

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-arm-kernel@lists.infradead.org
Fixes: 0361c7e5 ("ARM: ep93xx: multiplatform support")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>