cw1200: Fix a signedness bug in cw1200_load_firmware()

commit 4a50d454502f1401171ff061a5424583f91266db upstream.

The "priv->hw_type" is an enum and in this context GCC will treat it
as an unsigned int so the error handling will never trigger.

Fixes: a910e4a9 ("cw1200: add driver for the ST-E CW1100 & CW1200 WLAN chipsets")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>