staging: vme: fix memory leak in vme_user_probe()

If vme_master_request() returns NULL when it failed,
it need to free buffers for master.

And also removes unreachable code in vme_user_probe().

Signed-off-by: Daeseok Youn <daeseok.youn@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>