target_files: Package pvmfw.bin under PVMFW/

Add the pvmfw.bin binary to the target_files archive to bring back
ATC-based change detection for pvmfw (which compares the content of
PVMFW/ between builds) and therefore bring back our TreeHugger
pre-submit tests for it. Those were introduced in c7b83787 ("Create
$(zip_root)/PVMFW & archive prebuilt used") but inadvertently removed
in d0000048 ("core: Get pmvfw.img partition from Soong").

Bug: 261393794
Test: m target-files-package
Change-Id: I0141d59154b54641cb348af3b98fe12624d5939e