ARM: 5870/1: arch/arm: Fix build failure for defconfigs without CONFIG_ISA_DMA_API set

A lot of ARM-defconfigs (those without CONFIG_ISA_DMA_API set) fail to
build [1][2][3] due to the changes of the patch
    [PATCH] PCI: Clean up build for CONFIG_PCI_QUIRKS unset
    by Rafael J. Wysocki (Sat, 2 Jan 2010 22:57:24 +0100) [4]
as the referenced variable 'isa_dma_bridge_buggy' in asm/dma.h is
enclosed by the CONFIG_ISA_DMA_API conditional all configs without this
setting fail to build.

I'm not sure wether moving the condition is the right way to solve the
issue, but atleast it fixes the issue :)

References:
[1] http://kisskb.ellerman.id.au/kisskb/buildresult/1983354/
[2] http://kisskb.ellerman.id.au/kisskb/buildresult/1983333/
[3] http://kisskb.ellerman.id.au/kisskb/buildresult/1983337/
[4] http://lkml.org/lkml/2010/1/2/102

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>