drm/nouveau: Fix module parameter description formats

Module parameter descriptions don't take a trailing \n, otherwise it
breaks formatting of modinfo's output. Also remove trailing space.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: David Airlie <airlied@linux.ie>
Cc: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>