PAN: Always allocate in bta_pan_data_buf_ind_cback

Change I63b857d031c55d3a0754e4101e330843eb422b2a caused a double
free.  Move the free call to pan_data_buf_ind_cb().

Free the buffer before every return in pan_data_buf_ind_cb.

Bug: 74950468
Test: manual tethering test with DUT sharing its connection
Change-Id: If4526f3042699581e2cdde79a362eef0f83768eb
Merged-In: If4526f3042699581e2cdde79a362eef0f83768eb