mfd: twl-core: Disable IRQ while suspended

Since commit 6e2bd956936 ("i2c: omap: Use noirq system sleep pm ops to idle device for suspend")
on gta04 we have handle_twl4030_pih() called in situations where pm_runtime_get()
in i2c-omap.c returns -EACCES.

[   86.474365] Freezing remaining freezable tasks ... (elapsed 0.002 seconds) done.
[   86.485473] printk: Suspending console(s) (use no_console_suspend to debug)
[   86.555572] Disabling non-boot CPUs ...
[   86.555664] Successfully put all powerdomains to target state
[   86.563720] twl: Read failed (mod 1, reg 0x01 count 1)
[   86.563751] twl4030: I2C error -13 reading PIH ISR
[   86.563812] twl: Read failed (mod 1, reg 0x01 count 1)
[   86.563812] twl4030: I2C error -13 reading PIH ISR
[   86.563873] twl: Read failed (mod 1, reg 0x01 count 1)
[   86.563903] twl4030: I2C error -13 reading PIH ISR

This happens when we wakeup via something behing twl4030 (powerbutton or rtc
alarm). This goes on for minutes until the system is finally resumed.
Disable the irq on suspend and enable it on resume to avoid
having i2c access problems when the irq registers are checked.

Fixes: 6e2bd956936 ("i2c: omap: Use noirq system sleep pm ops to idle device for suspend")
Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
Tested-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>