Bluetooth: Kconfig: Remove redundant 'default n' declarations

All boolean options default to 'n' without the need to explicitly
state this. It's only the cases where we want 'default y' where we
need to state this.

Change-Id: I47dbda62462ea437a2423b8508ea2cc640a22e41
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>