drm/nouveau: Parse old style perf tables.

Used on nv17-nv28, they contain memory clocks and timings, only one of
the table entries can actually be used, depending on the RAMCFG
straps, and it's usually higher than the frequency programmed on boot
by the BIOS.

The memory timings listed in table version 0x1x are used to init the
0x12xx range but they aren't required for reclocking to work.

Signed-off-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>