msm: ipa3: Check input parameter before de-referencing it

At ipa3_usb_xdci_connect() we de-reference an input pointer
before validating it. This code switches the order.

Change-Id: I712c74c976c848c350cac9fe630120c48361720d
Signed-off-by: Ghanim Fodi <gfodi@codeaurora.org>