ARM: 5988/1: pgprot_dmacoherent() for non-mmu builds

Commit 26a26d32 ("dma-mapping: switch
ARMv7 DMA mappings to retain 'memory' attribute") added a new macro,
pgprot_dmacoherent(), to correctly map DMA memory. The non-mmu pgtable
support code also needs to implement this macro, otherwise when
compiling you get:

  CC      arch/arm/mm/dma-mapping.o
arch/arm/mm/dma-mapping.c: In function 'dma_alloc_coherent':
arch/arm/mm/dma-mapping.c:320: error: implicit declaration of function 'pgprot_dmacoherent'
arch/arm/mm/dma-mapping.c:320: error: 'pgprot_kernel' undeclared (first use in this function)
arch/arm/mm/dma-mapping.c:320: error: (Each undeclared identifier is reported only once
arch/arm/mm/dma-mapping.c:320: error: for each function it appears in.)

Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>