Migrate mpq demux driver from kernel 4.9 to 4.14

This change migrates all the relevant files and updates made
to the dvb/demux framework, required for mpq demux driver.

The snapshot is taken as of msm-4.9,
'commit ba29a3e82c501 ("Migrate mpq demux driver from kernel 4.4 to 4.9")'
In addition, introduce a few code changes to fix warnings,
typos and other style issues.

Change-Id: I1621409bfbdbbec676a6ba29c0583c80574a4945
Signed-off-by: Monika Singh <monising@codeaurora.org>