staging: rtl8188eu: fix missing unlock on error in rtw_resume_process()

Add the missing unlock before return from function
rtw_resume_process() in the error handling case.

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>