soc: qcom: smd: Support multiple of 32 SMD fifo size

In current code the SMD FIFO size is expect to be power of two
and the read_avail and write_avail calculation are based on
fifo_mask which will not work if the SMD FIFO size is not power
of two.

Add code to support SMD FIFO sizes which are multiple of 32 and
update the read_avial and write_avail code accordingly.

CRs-Fixed: 688362
Change-Id: I4425166aace6509e5f5ce75c9f949bc30a56a54a
Signed-off-by: Arun Kumar Neelakantam <aneela@codeaurora.org>