staging: rts5208: fix error return code in rtsx_probe()

Fix to return -ENOMEM instead of 0 when the memory alloc fail
in probe error handling path.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>