ssb: Fix error routine when fallback SPROM fails

When there is a CRC error in the SPROM read from the device, the code
attempts to handle a fallback SPROM. When this also fails, the driver
returns zero rather than an error code.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Stable <stable@vger.kernel.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>