sfxge: cleanup: report error on failure path in efx_vpd_hunk_verify

If the VPD is corrupt and contains an 'RV' keyword before the
END tag, then this function could return without setting the
return code to report the error.

Found by prefast.

Submitted by: Andy Moreton <amoreton at solarflare.com>
Sponsored by: Solarflare Communications, Inc.
MFC after: 2 days