powerpc/mm: Wire up ioremap_cache()

The default implementation of ioremap_cache() is aliased to ioremap().
On powerpc ioremap() creates cache-inhibited mappings by default which
is almost certainly not what you wanted.
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/io.h

@@ -759,6 +759,8 @@ extern void __iomem *ioremap_prot(phys_addr_t address, unsigned long size,
 extern void __iomem *ioremap_wc(phys_addr_t address, unsigned long size);
 #define ioremap_nocache(addr, size)	ioremap((addr), (size))
 #define ioremap_uc(addr, size)		ioremap((addr), (size))
+#define ioremap_cache(addr, size) \
+	ioremap_prot((addr), (size), pgprot_val(PAGE_KERNEL))
 
 extern void iounmap(volatile void __iomem *addr);