drm/msm/sde: fix race condition between clk disable and interrupt handler

During idle power collapse/suspend cases, the driver disables all the
interrupts as part of the disable sequence and clks/resources are turned
off. The driver does not expect any interrupts after this. However there
might be a race condition between the interrupt handler and the disable
sequence as these two happens in difference contexts and are not
protected. If interrupts are serviced after clk disable, it would result
in unclocked register access error.
This change disables the interrupt line on power collapse/suspend so no
interrupt requests are received and enables the interrupt line on resume.

Change-Id: I0540716bdab56a0a6269efccb2c06408d3dcaa31
Signed-off-by: Harsh Sahu <hsahu@codeaurora.org>