Input: synaptics - fix wrong dimensions check

The commit 83ba9ea8 ommitted the return
line for the old synaptics model accidentally.  This resulted in a wrong
check, namely, the dimensions are checked for the old devices that don't
support the query properly.

This patch adds the return line back.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>