[coreboot] unrv2b delay (v2)

[Arne Georg Gleditsch]

Hi,

The unrv2b uncompression algorithm appears to behave very badly in the
absence of a proper cache.  Instrumentation indicates somehting like ~180
i-stream cacheline requests for _every_ d-stream cacheline request
during decompression.  The following patch copies the unrv2b function to
DRAM before performing the actual decompression, reducing the run-time
from 12.5s to 50ms in my environment.  The patch is somewhat rough, and
assumes that (1) the unrv2b function is less than 1k in size, and (2)
that placing a copy of the function just after the decompress
destination is unproblematic.  It works well for me, though.

Signed-off-by: Arne Georg Gleditsch