binder: fix offset calculation in debug log

The vma start address should be substracted from the buffer's user data
address and not the other way around.

Cc: Tiffany Y. Yang <ynaffit@google.com>
Cc: stable <stable@kernel.org>
Fixes: 162c7973 ("binder: avoid user addresses in debug logs")
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Reviewed-by: Tiffany Y. Yang <ynaffit@google.com>
Link: https://lore.kernel.org/r/20250325184902.587138-1-cmllamas@google.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>