[system][bt] fix -Wreorder-init-list

C++20 will require members in a designated initializer to be in order
unlike C99.

Bug: 139945549
Test: mm
Change-Id: I62dd309d5749c74c18e4291e7d1cef1f3587bf41
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>