rsi: fix potential null dereference in rsi_probe()

The id pointer can be NULL in rsi_probe(). It is checked everywhere except
for the else branch in the idProduct condition. The patch adds NULL check
before the id dereference in the rsi_dbg() call.

Fixes: 54fdb318

 ("rsi: add new device model for 9116")
Cc: Amitkumar Karwar <amitkarwar@gmail.com>
Cc: Siva Rebbagondla <siva8118@gmail.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Denis Efremov <efremov@linux.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>