shooteru: Clean up

Remove prebuilt kernel and modules
Remove unneeded compile flags (most of them were orphaned)
Remove unneeded kernel headers and firmware symlinks from init.shooteru.rc

Change-Id: I6425f00b74bcecb8a9e393cea8fc4dffc33dda48
Signed-off-by: helicopter88 <johnlemon.lol@gmail.com>