Bluetooth: Add reference counting for buffers

In certain scenarios we want to keep the buffers around for longer
and avoid the default bt_buf_put() calls from putting them back to the
available buffers queue. This patch adds reference counting for the
buffers, along with a bt_buf_hold() API to increment the reference
count. Now bt_buf_put() will only put the buffer back to the pool if
the reference count hits 0.

Change-Id: I1590c5574e18600939f55e5339a6da3d061f7682
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
2 files changed