airo: fix memory leaks

In proc_BSSList_open(), 'file->private_data' is allocated through kzalloc()
and 'data->rbuffer' is allocated through kmalloc(). In the following
execution, if an error occurs, they are not deallocated, leading to memory
leaks. To fix this issue, free the allocated memory regions before
returning the error.

Signed-off-by: Wenwen Wang <wenwen@cs.uga.edu>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>