p54spi: Add error message for eeprom failure

This adds an error message for the eeprom request failure
case. This way it's easier for the user to figure out
what went wrong.

Signed-off-by: Michael Büsch <mb@bu3sch.de>
Acked-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>