slim_msm: Report flow-error and mask apps slimbus port interrupts

Apps side slimbus ports may overflow/underflow if BAM pipes connected
to those ports don't have descriptors scheduled.
Report such errors and mask the port interrupts until BAM pipes have
descriptors scheduled to avoid interrupts firing multiple times.

Signed-off-by: Sagar Dharia <sdharia@codeaurora.org>
Signed-off-by: Dan Trifan <jimsth@gmail.com>