Floss: fix MSBC temp packet decode buffer size

In CL:2989709 there was a change to allow packet size of 24, but
CL:2899167 assumed the packet size is always greater than 60 (a SCO
packet size), and this causes heap buffer overflow.

Bug: 332349377
Tag: #floss
Flag: EXEMPT floss only changes
Test: m Bluetooth && atest --host net_test_stack_btm # with CL:3002551
Change-Id: Ic5923f6ca250d0db20df054ffbd6abd069fd94a3