USB: gadget: ci13xx_pci: remove unneeded check in ci13xxx_pci_probe()

As pointed out by Dan Carpenter, the check for NULL for the id variable
is no longer needed, especially as we just dereferenced it a few lines
earlier, causing an oops if it really was NULL.

This was caused by 62bb84ed: "usb: gadget: ci13xxx: convert to
platform device".

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>