Bluetooth: SDP: Introduce ContinuationState of PDU

Adds initial handling of PDU Continuation State. It has crutial role
to interact with SDP server when receiving partial SDP PDU responses.

< ACL Data TX: Handle 77 flags 0x00 dlen 24
      Channel: 64 len 20 [PSM 1 mode 0] {chan 0}
      SDP: Service Search Attribute Request (0x06) tid 3 len 15
        Search pattern: [len 5]
          Sequence (6) with 3 bytes [8 extra bits] len 5
            UUID (3) with 2 bytes [0 extra bits] len 3
              OBEX Object Push (0x1105)
        Max record count: 65535
        Attribute list: [len 7]
          Sequence (6) with 5 bytes [8 extra bits] len 7
            Unsigned Integer (1) with 4 bytes [0 extra bits] len 5
              0x0000ffff
        Continuation state: 0
> HCI Event: Number of Completed Packets (0x13) plen 5
        Num handles: 1
        Handle: 77
        Count: 1
> ACL Data RX: Handle 77 flags 0x02 dlen 68
      Channel: 64 len 64 [PSM 1 mode 0] {chan 0}
      SDP: Service Search Attribute Response (0x07) tid 3 len 59
        Attribute bytes: 48
        Continuation state: 8
        8d 55 59 58 30 00 00 00                          .UYX0...

Jira: ZEP-1112

Change-Id: I53ea9ae64c3f2685c9a12be3683dfc3a95aa8bf9
Signed-off-by: Arkadiusz Lichwa <arkadiusz.lichwa@tieto.com>