Added SPDX-license-identifier-Apache-2.0 to:
  Android.bp
  frameworks/PlatformLibrary/Android.bp
  frameworks/PlatformLibrary/Android.mk
  frameworks/PlatformLibrary/jni/Android.mk

Bug: 68860345
Bug: 151177513
Bug: 151953481

Test: m all

Exempt-From-Owner-Approval: janitorial work
Change-Id: I50b528ccc25f5feaf5ad1f8b6879b7d45ee1643c