libhwc2.1: Replace TARGET_SOC with TARGET_BOARD_PLATFORM

TARGET_SOC is vendor-defined, while TARGET_BOARD_PLATFORM is recognized
by the build system. Currently, both are set to the same value.

This change deprecates the former variable in favor of the latter.

Bug: 150506183
Test: No difference in build output file listing after a clean build of
    aosp_slider.
Change-Id: Ib3a3f109113180c1a0fc2f6b460351ad246804a1
1 file changed
tree: 03592f91976f116801187b10d4c7261ac8d60a88
  1. libhwc2.1/