mmc: omap_hsmmc: trivial cleanups

A bunch of non-functional cleanups to the omap_hsmmc driver.

It basically decreases indentation level, drop unneded dereferences
and drop unneded accesses to the platform_device structure.

Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Venkatraman S <svenkatr@ti.com>
Signed-off-by: Chris Ball <cjb@laptop.org>