Staging: epl: clean up demo_main.c

Fix some static symbols and drop the kernel version checks.

Also comment out the init and exit functions, as they don't get used
anymore.

Cc: Daniel Krueger <daniel.krueger@systec-electronic.com>
Cc: Ronald Sieber <Ronald.Sieber@systec-electronic.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>