UBUNTU: Support copying of atags in the decompressor.
This is needed if this kernel is booted using kexec-hardboot[1],
because atags need to be in direct-mapped region, usually
the first 16kB of RAM.

Ported from Jens Andersen <jens.andersen@gmail.com>'s
kernel for Asus TF201 [2].

[1] Hardboot: http://forum.xda-developers.com/showthread.php?t=1266827
[2] Original repository: http://git.io/EXpn2A
UBUNTU: Enable caching and buffering of whole RAM in the decompressor
This is to speed-up booting if this kernel is booted using
kexec-hardboot[1]. Without this patch, decompressor is very slow
to decompress, because it is located far above the kernel destination.

Ported from Jens Andersen <jens.andersen@gmail.com>'s
kernel for Asus TF201 [2].

[1] Hardboot: http://forum.xda-developers.com/showthread.php?t=1266827
[2] Original repository: http://git.io/EXpn2A