drivers: fix up various ->llseek() implementations

Fix up a few ->llseek() implementations that won't deal with SEEK_HOLE/SEEK_DATA
properly.  Make them future proof so that if we ever add new options they will
return -EINVAL.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>