msm: ep_pcie: Change perst irq from edge to level

Change perst irq from edge to level to prevent unwanted
system wakeups due to probable noise on the perst gpio.
Also modify the trigger level based on the expected
value (level) of the gpio.

Change-Id: I83be49c0a50d08e143caf70ecfbba6dbf94cd6b2
Signed-off-by: Siva Kumar Akkireddi <sivaa@codeaurora.org>