msm: pcie: update IRQ locks

Add IRQ lock for PCIe global interrupt handler.
Remove redundant locks in other IRQ handlers. Do
not service PCIe global interrupt when turning
off the link.

Change-Id: I402c1321db3afff0f7dda7c075a91669ec2cc038
Signed-off-by: Tony Truong <truong@codeaurora.org>