EDAC/amd64: Support more than two controllers for chip select handling

The struct chip_select array that's used for saving chip select bases
and masks is fixed at length of two. There should be one struct
chip_select for each controller, so this array should be increased to
support systems that may have more than two controllers.

Increase the size of the struct chip_select array to eight, which is the
largest number of controllers per die currently supported on AMD
systems.

Also, carve out the Family 17h+ reading of the bases/masks into a
separate function. This effectively reverts the original bases/masks
reading code to before Family 17h support was added.

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Tested-by: Kim Phillips <kim.phillips@amd.com>
Cc: James Morse <james.morse@arm.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: https://lkml.kernel.org/r/20190228153558.127292-5-Yazen.Ghannam@amd.com