driver: Make add_sentinel a "real" inline function

Putting an inline function in a .c file does not do anything except
confuse the compiler.  Newer versions of gcc will complain loudly about
this, and refuse to build, so put the function in a .h file so that it
can actually be used as an inline function, making everyone happy.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
driver/ppm_types.h: delete the file

It's not needed (kernel code isn't going to be built on other
platforms), so just directly include <linux/types.h> in the .h files
instead.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
driver: properly predefine variables

Two variables were defined in ppm.h, but the .c files that declared them
did not include ppm.h, making sparse complain about these.  Properly
include the .h file, and move 2 structures that are only used in main.c,
into main.c to avoid having to have a bunch of .h files in ppm.h that
are not needed.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Merge pull request #20 from gregkh/kernel_code_style

Build fixes for newer versions of gcc, and some minor cleanups.