USB: serial: fix regression in Visor/Palm OS module for kernels >= 2.6.24

Fixes a bug/inconsistency revealed by the additional sanity checking in
   commit 063a2da8


introduced in the original 2.6.24 branch.

The Handspring Visor / PalmOS 4 device structure defines .num_bulk_out=2
but the usb-serial probe returns num_bulk_out=3, triggering the check in
the above commit and forcing a bail out when the device (a Garmin iQue in
my case) attempts to connect.  The patch bumps the expected number of
endpoints to 3.

FWIW, this patch will probably solve the following kernel bug report for
Treo users (identical symptoms, different model PalmOS units):
  <http://bugzilla.kernel.org/show_bug.cgi?id=10118>


Signed-off-by: Brad Sawatzky <brad+kernel@swatter.net>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>