staging: android: ion: Fix error handling in ion_query_heaps()

If the copy_to_user() fails we should unlock and return directly without
updating "cnt".  Also the return value should be -EFAULT instead of the
number of bytes remaining.

Fixes: 02b23803 ("staging: android: ion: Add ioctl to query available heaps")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>