[ARM] 4569/1: ep93xx_gpio_irq_type(): fix spurious enumeration offset for FGPIO handling

The EP93XX_GPIO_LINE_F() macro is supposed to be called with a line
number between 0 and 7, but the current code causes it to get called
with an spuriously offset number range {16..23}.

Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>
Signed-off-by: Lennert Buytenhek <kernel@wantstofly.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>