ANDROID: initramfs: call free_initrd() when skipping init

Memory allocated for initrd would not be reclaimed if initializing ramfs
was skipped.

Bug: 69901741
Test: "grep MemTotal /proc/meminfo" increases by a few MB on an Android
device with a/b boot.

Change-Id: Ifbe094d303ed12cfd6de6aa004a8a19137a2f58a
Signed-off-by: Nick Bray <ncbray@google.com>