msm: vidc: Re-enable IRQ even if we didn't do anything in the IRQ handler

Since we disable the IRQ unconditionally in the IRQ handler, we need to
do likewise in the bottom-half of the interrupt handling routine.
Otherwise, if __power_on() fails, we end up never re-enabling the IRQ,
which eventually results in the next session timing out.

Change-Id: I010c7ebc40d13c310229fa4c06c01259de68f124
Signed-off-by: Deva Ramasubramanian <dramasub@codeaurora.org>