dt-bindings: net: bluetooth: update broadcom-bluetooth

Add documentation for brcm,bt-pcm-int-params vendor specific
configuration of the SCO PCM settings.

Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>