[U-Boot] u-boot ppc does not work with gcc 4.8

[Dirk Eibach]

In my latest u-boot builds I had some strange behaviour that I finally
tracked down to not fixed up flash addresses in relocated u-boot.
These addresses come from symbols in the .data.rel.ro.local section
that is not handled by u-boot linker scripts at the moment.

Some background on relro: http://www.airs.com/blog/archives/189

Joerg Albert already inquired about this on the gcc ML:
https://gcc.gnu.org/ml/gcc-help/2014-02/msg00017.html and he already
suggested a solution:
https://gcc.gnu.org/ml/gcc-help/2014-02/msg00054.html

So there a three things to notice:
1. Do not use gcc 4.8 and u-boot at the moment.
2. You might not notice that you have a problem until you erase u-boot
from flash (and get your cache flushed).
3. Handling relro properly should be on the TODO-List

Maybe this is already common knowledge an maybe somebody is already
working on this - but I did not notice yet. So in this case: sorry for
the noise :)

Cheers
Dirk