gpio-tz1090: convert to use generic irqchip

Convert gpio-tz1090 driver to use generic irqchips. This allows the
irq_ack, irq_mask, and irq_unmask callbacks and associated helper
functions to be removed. Also switch to using irq_setup_alt_chip() in
the irq_set_type callback instead of using __irq_set_handler_locked().

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Grant Likely <grant.likely@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>