[coreboot] [RFC] change the ROM caching for AMD CAR

[Rudolf Marek]

Hi all,

It looks like we can cache now the whole ROM while in CAR (i showed that in the 
analysis posted earlier, it works too ;)

The attached patch does that. Comments?

Marc and I thinks we can add some safeguard to check if any L2 data was evicted 
during CAR to RAM. This is just few instructions to enable the PerfCounter and
then  read it in the post_cache_as_ram. I will post this as separate patch.

Signed-off-by: Rudolf Marek

I did not test this particular patch however it does work with similar changes 
already. I take this patch as think for RFC, if it is enough to change it like this.

Thanks,
Rudolf