USB: msm72k_otg: Block notifying pmic about current drawn multiple times

In some cases, due to spurious interrupts, we may end up in notifying the
amps of current to be drawn to the PMIC multiple times.

Handle such cases by comparing the previously updated data to the PMIC with
the present data.

CRs-Fixed: 309178
Change-Id: I4025e166dff0bc6698e786226f5766807050300c
Signed-off-by: Rajkumar Raghupathy <raghup@codeaurora.org>