net: intel: iavf: fix error return code of iavf_init_get_resources()

When iavf_process_config() fails, no error return code of
iavf_init_get_resources() is assigned.
To fix this bug, err is assigned with the return value of
iavf_process_config(), and then err is checked.

Reported-by: TOTE Robot <oslab@tsinghua.edu.cn>
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>