gpio: spear_gpio: Fix gpio_set_value() implementation

gpio: spear_gpio: Fix gpio_set_value() implementation

In current gpio_set_value() implementation, it always sets the gpio control bit
no matter the value argument is 0 or 1. Thus the GPIOs never set to low.
This patch fixes this bug.

The address bus is used as a mask on read/write operations, so that independent
software drivers can set their GPIO bits without affecting any other pins in a
single write operation. Thus we don't need a read-modify-write to update the
register.

Signed-off-by: Axel Lin <[email protected]>
Acked-by: Stefan Roese <[email protected]>
Reviewed-by: Vipin Kumar <[email protected]>
Reviewed-by: Michael Trimarchi <[email protected]>