mmc: sdhci: avoid sync'ing the SG if there's no misalignment

On read, we don't need to sync the whole scatterlist and then check
whether any segments need copying - if we check first, we avoid
potentially expensive cache handling.

CRs-fixed: 684185
Change-Id: I9a07b1b1e83d0299765f80adc14bbff44f7ed114
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Tested-by: Markus Pargmann <mpa@pengutronix.de>
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <chris@printf.net>
Git-commit: de0b65a786ae83c8f6dfb712f65b9a36af70a981
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[venkatg@codeaurora.org: use align_bytes - 1 for alignment check]
Signed-off-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>