TWL4030: clear TWL GPIO interrupt status registers

twl_init_irq() does not clear the TWL GPIO ISR registers, but the PIH
ISR thinks that it has.  This causes any previously-latched GPIO interrupts
to be stuck on until twl4030-gpio.c initializes, often drowning the console in

    TWL4030 module irq 368 is disabled but can't be masked!

messages.  This seems to be a particular problem when booting on Beagle.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>