vxge: Handle errors in vxge_hw_vpath_fw_api

Propagate the return code of the call to vxge_hw_vpath_fw_api and
__vxge_hw_vpath_pci_func_mode_get.  This enables the proper handling of
error conditions when querying the function mode of the device during
probe.

Signed-off-by: Jon Mason <jon.mason@exar.com>
Signed-off-by: Ram Vepa <ram.vepa@exar.com>
Signed-off-by: David S. Miller <davem@davemloft.net>