Add Sparse checking to kernel module builds

Sparse is a semantic checker for C that can help find potential issues
in the kernel module code. To make use of the tool, the CMake files for
the kernel modules have been updated to enable the tool to run on all
the kernel module source files before they are built.

Change-Id: I114920448763b69eb0bdfb9ab6ec51ea8b940881
Signed-off-by: Mikael Olsson <mikael.olsson@arm.com>