qcom: fg-memif: add support for using IMA single mode

Currently, based on the number of bytes read/written, IMA is
configured for single or burst mode. Add an option to override
to single mode whenever required.

While at it, change pr_err() statements to print some more debug
information which might be useful.

Change-Id: If19e135ed4014732a0efe56250f56f0760a1fb93
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>