ARM: tegra20: implement BCT patching

This function allows updating bootloader from u-boot
on production devices without need in host PC.

Be aware! It works only with re-crypt BCT.

Tested-by: Robert Eckelmann <longnoserob@gmail.com> # ASUS TF101 T20
Signed-off-by: Ramin Khonsari <raminterex@yahoo.com>
Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
Signed-off-by: Tom <twarren@nvidia.com>