[PATCH] spidernet: check if firmware was loaded correctly

Uploading the device firmware may fail if wrong input data
was provided by the user. This checks for the condition.

From: Jens Osterkamp <Jens.Osterkamp@de.ibm.com>
Signed-off-by: Jens Osterkamp <Jens.Osterkamp@de.ibm.com>
Signed-off-by: Arnd Bergmann <arndb@de.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>