This will be used by the user to disconnect or cancel connect dlc.
This also defines an internal close function which will take
appropriate action based on the dlc state.
In case of user initiated disconnection if some pending packets are
there in queue then it has to be sent before sending DISC packet.
< ACL Data TX: Handle 256 flags 0x00 dlen 8
Channel: 64 len 4 [PSM 3 mode 0] {chan 0}
RFCOMM: Disconnect (DISC) (0x43)
Address: 0x2b cr 1 dlci 0x0a
Control: 0x53 poll/final 1
Length: 0
FCS: 0x6d
> ACL Data RX: Handle 256 flags 0x02 dlen 8
Channel: 64 len 4 [PSM 3 mode 0] {chan 0}
RFCOMM: Unnumbered Ack (UA) (0x63)
Address: 0x29 cr 0 dlci 0x0a
Control: 0x73 poll/final 1
Length: 0
FCS: 0x26
Change-Id: Ie4fa3bd8f6b279fee6fb56ddce198d82c5047849
Signed-off-by: Jaganath Kanakkassery <jaganathx.kanakkassery@intel.com>