gpio/omap: remove unnecessary bit-masking for read access

Remove un-necessary bit masking. Since the register are 4 byte aligned
and readl would work as is. The 'enabled' mask is already taking care
to mask for bank width.

Signed-off-by: Charulatha V <charu@ti.com>
Signed-off-by: Tarun Kanti DebBarma <tarun.kanti@ti.com>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>