Fix strict-aliasing warning in dlmalloc

Fix strict-aliasing warning in dlmalloc

This fixes the following warnings in dlmalloc seen with my gcc 4.6.

dlmalloc.c: In function 'malloc_bin_reloc':
dlmalloc.c:1493: warning: dereferencing pointer 'p' does break strict-aliasing rules
dlmalloc.c:1493: warning: dereferencing pointer 'p' does break strict-aliasing rules
dlmalloc.c:1490: note: initialized from here
dlmalloc.c:1493: note: initialized from here

This version is tested on avr32 arch boards.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>