mmc: omap_hsmmc: remove unused vars and includes

Some straight forward cleanup of unnecessary #include's and host
variables. Some of the verbose and redundant debug messages are
converted to use dev_vdbg.

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