Cleanup dependencies of debug boot images

Remove redundant dependencies and adjust build rule, so that
  ramdisk-debug.img is built iff. boot-debug.img is built
same adjustment for vendor_boot-debug.img, boot-test-harness.img,
vendor_boot-test-harness.img.

Also remove "rsync" build rule in test harness ramdisk.

Bug: 201753847
Test: PRODUCT_BUILD_DEBUG_BOOT_IMAGE=true \
  PRODUCT_BUILD_DEBUG_VENDOR_BOOT_IMAGE=false \
  => ramdisk-debug.img is built; vendor_ramdisk-debug.img is not
Test: PRODUCT_BUILD_DEBUG_BOOT_IMAGE=false \
  PRODUCT_BUILD_DEBUG_VENDOR_BOOT_IMAGE=true \
  => ramdisk-debug.img is not built; vendor_ramdisk-debug.img is
Test: PRODUCT_BUILD_DEBUG_BOOT_IMAGE=true \
  PRODUCT_BUILD_DEBUG_VENDOR_BOOT_IMAGE=true \
  => ramdisk-debug.img is built; so do vendor_ramdisk-debug.img
Change-Id: I33f526bd3c50b9c4010f46e490cab778fcb23371