EDAC: Drop per-memory controller buses

... and use the single edac_subsys object returned from
subsys_system_register(). The idea is to have a single bus
and multiple devices on it.

Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
CC: Aristeu Rozanski Filho <arozansk@redhat.com>
CC: Greg KH <gregkh@linuxfoundation.org>
CC: Justin Ernst <justin.ernst@hpe.com>
CC: linux-edac <linux-edac@vger.kernel.org>
CC: Mauro Carvalho Chehab <mchehab@kernel.org>
CC: Russ Anderson <rja@hpe.com>
Cc: Tony Luck <tony.luck@intel.com>
Link: https://lkml.kernel.org/r/20180926152752.GG5584@zn.tnic

drivers/edac/edac_mc.c

@@ -55,8 +55,6 @@ static LIST_HEAD(mc_devices);
  */
 static const char *edac_mc_owner;
 
-static struct bus_type mc_bus[EDAC_MAX_MCS];
-
 int edac_get_report_status(void)
 {
 	return edac_report;
@@ -716,11 +714,6 @@ int edac_mc_add_mc_with_groups(struct mem_ctl_info *mci,
 	int ret = -EINVAL;
 	edac_dbg(0, "\n");
 
-	if (mci->mc_idx >= EDAC_MAX_MCS) {
-		pr_warn_once("Too many memory controllers: %d\n", mci->mc_idx);
-		return -ENODEV;
-	}
-
 #ifdef CONFIG_EDAC_DEBUG
 	if (edac_debug_level >= 3)
 		edac_mc_dump_mci(mci);
@@ -760,7 +753,7 @@ int edac_mc_add_mc_with_groups(struct mem_ctl_info *mci,
 	/* set load time so that error rate can be tracked */
 	mci->start_time = jiffies;
 
-	mci->bus = &mc_bus[mci->mc_idx];
+	mci->bus = edac_get_sysfs_subsys();
 
 	if (edac_create_sysfs_mci_device(mci, groups)) {
 		edac_mc_printk(mci, KERN_WARNING,