omap_hsmmc: consider MMC_PM_KEEP_POWER on suspend/resume

When an mmc card has the MMC_PM_KEEP_POWER flag, it shouldn't
be powered off on suspend (and thus doesn't have to be powered-on
on resume)

While on it, change the suspend flow a bit, to make it a bit
easier to follow.

Signed-off-by: Eliad Peller <eliad@wizery.com>
Acked-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>