Change OFMEM to allocate memory from the top of RAM downwards.
At the moment OFMEM allocates memory from the bottom of RAM upwards, however many loaders/kernels initialise themselves in lower
memory areas which can cause them to be overwritten by subsequent memory allocations. Mimic the existing SPARC32 behaviour by
allocating physical and virtual memory from the top of RAM downwards.
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@siriusit.co.uk>
git-svn-id: svn://openbios.org/openbios/trunk/openbios-devel@996 f158a5a8-5612-0410-a976-696ce0be7e32