all: checkout lk to latest version built with libdram

The bootloader binaries are now built with libatf instead of the deprecated libdram.

lk is also linked to libatf and we discover that some boards doesn't behave correctly, we may have this kind of backtrace:

panic (caller 0xfffffff00020225c): die
HALT: action = 0, reason = 9
HALT: spinning forever..., ret = 0

lk project is not maintained anymore, not updated/built by CI and will be soon replaced.

Meanwhile we can checkout lk binaries to the latest known good state which was when lk was built with libdram.

All the lk binaries have been checkout like this:

$ git checkout 3a6ee738ffe4d5cc73fd1561da43d535e28a86b9 -- */lk-*.bin