mmc: omap_hsmmc: remove access to SYSCONFIG register

SYSCONFIG register of HSMMC IP is managed by the omap hwmod
abstraction layer. Resetting the IP and configuring the correct
SYSCONFIG mode is centrally managed by hwmod.

Remove code which manipulates IP reset and SYSCONFIG directly in
the driver.

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