mfd: Delay to mask tsc irq in max8925

There're two IRQ pins output from MAX8925. One is PMIC interrupt, the other
is TSC interrupt. But they're sharing one irq chip.

After initializing MAX8925 interrupts, unexpected TSC interrupt may occur and
it can't be cleared if touch driver isn't loaded.

Now move the operation of masking TSC interrupt behind requesting PMIC
interrupt. If touch driver isn't loaded, this interrupt is always masked.

Signed-off-by: Haojian Zhuang <haojian.zhuang@marvell.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>