msm: bam_dmux: use non-interruptable variants of wait_for_completion

Using interruptible variants of wait_forcompletion is unnecessary in
bam_dmux and adds useless complexity to the error handling code.
Move to non-interruptible variants to simplify things.

Change-Id: I8c9958ad3b43d4cb8c76d712abbdebdbd3ca32f1
Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>