ar5523: Add USB ID of SMCWUSBT-G2 wireless adapter

Add the required USB ID for running SMCWUSBT-G2 wireless adapter (SMC
"EZ Connect g").

This device uses ar5523 chipset and requires firmware to be loaded. Even
though pid of the device is 4507, this patch adds it as 4506 so that
AR5523_DEVICE_UG macro can set the AR5523_FLAG_PRE_FIRMWARE flag for pid
4507.

Signed-off-by: Mert Dirik <mertdirik@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>