Revert "rsi: fix potential null dereference in rsi_probe()"

This reverts commit f170d44b

.

USB core will never call a USB-driver probe function with a NULL
device-id pointer.

Reverting before removing the existing checks in order to document this
and prevent the offending commit from being "autoselected" for stable.

Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>