drivers/net/tlan.c: compilation warning fix

Add a check for the pci_register_driver() return value.  Removed unused
variable pad_allocated.

The aim of this patch is to remove the following warning messages:
drivers/net/tlan.c: In function 'tlan_probe':
drivers/net/tlan.c:486: warning: ignoring return value of 'pci_register_driver', declared with attribute warn_unused_result

Signed-off-by: Leonardo Potenza <lpotenza@inwind.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>