mfd: pmic8901: Fix section mismatches

WARNING: drivers/mfd/built-in.o(.text+0x3750): Section mismatch
in reference from the function pm8901_probe() to the function
.devinit.text:pm8xxx_irq_init()
The function pm8901_probe() references
the function __devinit pm8xxx_irq_init().
This is often because pm8901_probe lacks a __devinit
annotation or the annotation of pm8xxx_irq_init is wrong.

Change-Id: I4d6ea52fdacad73bed80e3f5be3e9e08cc49be65
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>