ARM: another fix for the DMA mapping checks

Peter reports that OMAP audio broke with the recent fix for these
checks, caused by OMAP audio using a long DMA mask.  We should
allow long DMA masks even with dma_addr_t if we can be sure
the amount of RAM we have won't allow the dma_addr_t to
overflow.  Unfortunately, the checks to detect overflow were not
correct.

Change-Id: I90d92ccf96eea7cad36739022c5179d6b98473de
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Git-commit: 9f28cde0bc643186d32744ce69d12222e8588fe7
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[ilialin@codeaurora.org: resolve trivial merge conflicts]
Signed-off-by: Ilia Lin <ilialin@codeaurora.org>