regulator: qpnp-regulator: Reset OCP count during voltage switch enable

Reset the OCP counter for voltage switches which use the OCP IRQ
in the qpnp_regulator_vs_enable callback function.  Resetting the
counter here ensures that a voltage switch is always able to
reach its final output voltage when a valid load is connected if
only one OCP event occurs while enabling the switch.

Change-Id: Ie5b2d5271c81ef4b3cb9c9d874ca66af5530ddc7
Signed-off-by: David Collins <collinsd@codeaurora.org>