gentpl.py: Fix issue where sometimes marker files have CPP defines

gentpl.py: Fix issue where sometimes marker files have CPP defines

When generating video.lst, modules whose marker file contains the string
VIDEO_LIST_MARKER are selected. But when the marker file contains the CPP
defines, one of the defines is VIDEO_LIST_MARKER and is present in all
marker files, so they are all selected. By removing the defines, the correct
modules are selected.

Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>