Revert^2 "Refactor sdk_car_md_x86_64.mk""

Reland the CL with the fix, the original CL breaks the build, because
it refers to the board in vendor/auto/embedded_board/ which are not
visible in AOSP.
Changes them to the boards under device/generic/car

This reverts commit 169e413aa66430a8a129da9dccdba227109abb7c.

Bug: 278320718
Test: it builds
Change-Id: Ifb4e1871e004a36d0e40d1237a4de0b8cc98c7fa
6 files changed