Update audio prebuilts to use Thumb instructions

This saves 168 KB in the installed image and should have zero to
slightly positive impact on performance.

Change-Id: Ice4da0bab81de6136a1533a6b1aca1d393854ffd
Don't allow /rom to be formatted in the recovery

/rom contains most of the information that specifically identifies the
device, so formatting it would be a Very Bad Idea [tm].

Change-Id: Ibcf5a847985b84aadbc34cf87a9a34cc1dee8ded