unicore32: add ioremap_nocache definition

Bugfix for following error messages:
lib/iomap.c: In function 'pci_iomap':
lib/iomap.c:274: error: implicit declaration of function 'ioremap_nocache'
lib/iomap.c:274: warning: return makes pointer from integer without a cast

Also see commit <f1ecc69838a2d7c8a3e1909f637d4083c071777d>
  it will hide the ioremap_nocache function for systems with an MMU

Signed-off-by: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Jonas Bonn <jonas@southpole.se>

arch/unicore32/include/asm/io.h

@@ -37,6 +37,7 @@ extern void __uc32_iounmap(volatile void __iomem *addr);
  */
 #define ioremap(cookie, size)		__uc32_ioremap(cookie, size)
 #define ioremap_cached(cookie, size)	__uc32_ioremap_cached(cookie, size)
+#define ioremap_nocache(cookie, size)	__uc32_ioremap(cookie, size)
 #define iounmap(cookie)			__uc32_iounmap(cookie)
 
 #define HAVE_ARCH_PIO_SIZE