Use the correct tBTA_PAN type when copying the data in a callback

This fixes stack-buffer-overflow issue found using ASAN.
Previously, the original data had type "struct tBTA_PAN_SET_ROLE"
and similar, and eventually "memcpy(..., sizeof(tBTA_PAN))" would
copy data beyond the end of the data buffer.

Bug: 36367964
Test: Running ASAN build
Change-Id: I47210a501378023168a0dd71381e93a5051a4c71