pcmcia: synclink_cs: fix error handling in mgslpc_probe()

mgslpc_probe() ignores errors in mgslpc_add_device() and
does not release all resource if mgslpc_config() failed.

The patch adds returned code to mgslpc_add_device()
and fixes the both issues.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>