EDAC/amd64: Read back the scrub rate PCI register on F15h

Commit:

  da92110d ("EDAC, amd64_edac: Extend scrub rate support to F15hM60h")

added support for F15h, model 0x60 CPUs but in doing so, missed to read
back SCRCTRL PCI config register on F15h CPUs which are *not* model
0x60. Add that read so that doing

  $ cat /sys/devices/system/edac/mc/mc0/sdram_scrub_rate

can show the previously set DRAM scrub rate.

Fixes: da92110d ("EDAC, amd64_edac: Extend scrub rate support to F15hM60h")
Reported-by: Anders Andersson <pipatron@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org> #v4.4..
Link: https://lkml.kernel.org/r/CAKkunMbNWppx_i6xSdDHLseA2QQmGJqj_crY=NF-GZML5np4Vw@mail.gmail.com