Bluetooth: Use unsigned int instead of signed int

The involved values are all unsigned and thus unsigned int should be
used instead of signed int. Assigning ~0 to a signed int results in -1,
which is confusing and error-prone, while the code is trying to set the
maximum value possible.

The code still works because the C standard defines that unsigned
comparison will be performed in these cases, when comparing an unsigned
int and a signed int.

Signed-off-by: Mikel Astiz <mikel.astiz.oss@gmail.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Gustavo Padovan <gustavo@padovan.org>