ARM: 6029/1: ep93xx: gpio.c: local functions should be static

The functions ep93xx_gpio_update_int_params and ep93xx_gpio_int_mask
are not exported and should be static.  This was overlooked when
moving the code from core.c.

Also, change a comment to better indicate what the code is for.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Ryan Mallon <ryan@bluewatersys.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>