AVRCP 1.6: Limit GetFolderItemResponse

Usecase:
1) Connect from AVRCP Controller supporting browsing
   having low L2CAP MTU eg 672.
2) Request for get folder items with large request items,
   response for which will exceed MTU size.

Expected Result:
As per AVRCP 1.6 Spec, section 29.20 pg 178, response should be
limited to number of completed get folder items that can fit in
single AVCTP Browsing channel MTU even if the completed items
are less than actually requested by AVRCP Controller.

Observation:
DUT responding with Internal Error.

Root Cause:
When there is no space to fill complete Get Folder Item response
within MTU size, DUT was returning error.

Fix:
Send max completed items which can fit in single MTU packet.

Test: Checked if the remote device can receive the truncated
response and get folder items succeeds when remote device
reissues get folder item request with updated start list count.

Frequency: 5/5

Bug: 37304477
Change-Id: I1963f97075382fc8333038e3efffaf61a9d84a28