ARM: locomo: fix locomo irq handling

Accidentally booting Collie on Assabet reveals that the locomo driver
incorrectly overwrites gpio-sa1100's chip data for its parent interrupt,
leading to oops in sa1100_gpio_unmask() and sa1100_update_edge_regs()
when "gpio: sa1100: convert to use IO accessors" is applied.  Fix locomo
to use the handler data rather than chip data for its parent interrupt.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>