msm: sps: check new pending IRQs before exit IRQ handler

New pipe IRQs may come when the IRQ handler is handling the exposed
IRQs on other pipes. Add the checking here to handle the new coming
IRQs.

CRs-fixed: 720964
Change-Id: Ic9377fbf74c399c5d5c0b500feef762e45ec0afb
Signed-off-by: Yan He <yanhe@codeaurora.org>