mmc: omap_hsmmc: cleanup omap_hsmmc_set_ios

No functional change. Move bus width configuration setting to a
separate function and invoke it only if there is a change in the
bus width.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>