pcmcia/electra_cf: Fix some return values in 'electra_cf_probe()' in case of error

'status' is known to be 0 at this point. It must be set to a meaningful
value in order to return an error code if one of the 'of_get_property()'
call fails.

Return -EINVAL in such a case.

Fixes: 2b571a06("pcmcia: CompactFlash driver for PA Semi Electra boards")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>