power: pm8921-charger: remove OV UV irq

Enabling the OverVoltage (OV) and UnderVoltage (UV) interrupts is
causing an interrupt storm. These interrupts are not used by the
charger driver.

Remove them from being registered and enabled.

Change-Id: I2605afc2d6f9f3569ec783b2d23881f31cc9038a
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>