skfp: testing the wrong variable in skfp_driver_init()

The intent here was to test if the allocation failed but we tested
"SharedMemSize" instead of "SharedMemAddr" by mistake.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: Jiri Pirko <jpirko@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>