msm: sps: Fix build warnings

Fix Sparse warnings to enable SPS driver for Lahaina - use
NULL instead of 0 to specify null argument, and use the static
keyword for locally used structures.

Change-Id: If6d69bb464b821e408d757317f7ed2ef15355f7f
Signed-off-by: Siva Kumar Akkireddi <sivaa@codeaurora.org>