gpio/omap: fix missing dataout context save in _set_gpio_dataout_reg

There are two functions, _set_gpio_dataout_reg() and _set_gpio_dataout_mask()
which writes to dataout register and the dataout context must be saved.
It is missing in the first function, _set_gpio_dataout_reg(). Fix this.

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>