mfd: wcd9xxx-irq: check if wcd9xxx_res irq is 0 before using it

During SSR, wcd9xxx_res irq lock is destroyed as part of resource
cleanup. If driver tries to access wcd9xxx_res irq lock before it's
initialized, it could cause crash. Check if wcd9xxx_res irq is 0
before using it to avoid crash.

CRs-Fixed: 1003482
Change-Id: I959caf7b305e965b84e8204168194bbfda72dc52
Signed-off-by: Meng Wang <mwang@codeaurora.org>