envsetup: fix 'mmm mka'

Change-Id: Ia5f3fb4813585df21c27ce0035fa3f2b7d6b73e7
(cherry picked from commit 4be035ea8e5c0aa733c38f83e9d0124169fcb942)
Revert "inline kernel dtb build"

This reverts commit 8609a0fb59fa3d943cd33137b0910ced41013102.
This is specific to a device (or vendor) and is confusing people
building for other 8974s. A more generic implementation is required,
and until then device-local mkbootimg overloads can/should be
used.

Change-Id: Ia582f9ca73d454da4ada894b489aea883d6f5186
(cherry picked from commit f3815b1e1819e92f79fc7efe58592e8ef0b52dd1)
Make the kernel image format parametric instead of a chain of if/elses

Change-Id: I54bfcdecb8647f7bcf744e72b2de19fcf4e4e7ac
(cherry picked from commit 95c59c0a66203407111ac55b5cebb8315392db38)