power: qpnp-bms: request interrupts at the end of probe

The current driver requests interrupts before it initializes other
data structures. This creates NULL pointer exceptions if an interrupt
triggers before the data structures are initialized.

Move requesting interrupts towards the end of the probe function, after
data structures are initialized.

CRs-Fixed: 506597
Change-Id: I94a524a0a1b8a5fa9372e414bcf36d8448fc1e4a
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>