btmon: fix segfault caused by buffer overflow

btmon: fix segfault caused by buffer overflow

Buffer overflow vulnerability in monitor/sdp.c SDP continuation handling
caused btmon to crash. This happens in global static buffer which makes
it non-trivial to exploit.

This is nasty bug in a way that this can be triggered also over the air
by sending malformed SDP Search Attribute request to device running
btmon.

This crash was foung by fuzzing btmon with AFL. Seems to be reproducible
also with Synopsys Defensics SDP Server suite.

Change-Id: Ie149945cd95f6686183944e358cf25b485c769c4
Signed-off-by: himanshu <h.himanshu@samsung.com>