Staging: cxt1e1: remove code guarded by GENERIC_HDLC_VERSION

Current linux kernel has GENERIC_HDLC_VERSION equal to 4, no need to
have dead code in-kernel which was there for ancient kernel versions.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>