btlinux: Fix sepolicy for split policy (Treble) builds

In full Treble builds, the btlinux HAL fails to build the sepolicy:

neverallow check failed at out/target/product/linaro_x86_64/obj/ETC/plat_sepolicy.cil_intermediates/plat_sepolicy.cil:4518
from system/sepolicy/public/domain.te:673
  (neverallow base_typeattr_55 base_typeattr_56 (file (execute execute_no_trans entrypoint)))
    <root>
    allow at out/target/product/linaro_x86_64/obj/ETC/nonplat_sepolicy.cil_intermediates/nonplat_sepolicy.cil:6054
      (allow hal_bluetooth_btlinux hal_bluetooth_btlinux_exec (file (read getattr map execute entrypoint open)))

Test: Build completes successfully
Change-Id: Ibb8dbe7f2ca823c87ae4404c40cdc35656c8e0af
Signed-off-by: Rob Herring <robh@kernel.org>