gpio/omap: fix bankwidth for OMAP7xx MPUIO

In all OMAP1 SoCs, the MPUIO bank width is 16 bits. But, in OMAP7xx,
it is wrongly initialised to 32. Fix this.

Signed-off-by: Charulatha V <charu@ti.com>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>