Pass kernel release file to check_vintf.

check_vintf now accepts a file that contains the full kernel
release string as the first half of --kernel. Use it.

With this patch, BOARD_KERNEL_VERSION can be a full kernel release
string like 5.4.42-something, or 5.4.42-android12-0-something.

The content of target_files/META/kernel_version.txt also contains the
full kernel release, not just the kernel version.

Bug: 161317193
Test: m check-vintf-all
Change-Id: I3b52639f557532077894d9356c745c16b41dd91c