[coreboot] typo in amdk8/raminit_f.c

[Ronald Hoogenboom]

Hi,

There is a typo in amdk8/raminit_f.c regarding the preprocessor symbol
QRANK_DIMM_SUPPORT in line 2208, which caused the protected code
fragment never to be included for compilation.
I guessed what the dimm_mask and sz.rank should have been (I'm not
familiar with the functionality of this piece of code).

Please review, anyone who is familiar (yhlu/mjones?).

Signed-off-by: Ronald Hoogenboom