wifi: iwlwifi: Fix some error codes

This saves the error as PTR_ERR(wifi_pkg).  The problem is that
"wifi_pkg" is a valid pointer, not an error pointer.  Set the error code
to -EINVAL instead.

Fixes: 2a808414

 ("iwlwifi: acpi: support reading and storing WRDS revision 1 and 2")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://msgid.link/9620bb77-2d7c-4d76-b255-ad824ebf8e35@moroto.mountain
Signed-off-by: Johannes Berg <johannes.berg@intel.com>