mfd: wm8997: Mark INTERRUPT_STATUS_2_MASK as readable
mfd: wm8997: Mark INTERRUPT_STATUS_2_MASK as readable

Technically this register is not used on wm8997 however the regmap core
requires a continuous block of IRQs. The simplest solution is just to
add the register.

Signed-off-by: Charles Keepax <8e4aa0015eb43ed5ca66aaca3fb498609e1e427c@opensource.wolfsonmicro.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs