ACPI: APEI: Enable APEI multiple GHES source to share a single external IRQ

X-Gene platforms describe multiple GHES error sources with the same
hardware error notification type (external interrupt) and interrupt
number.

Change the GHES interrupt request to support sharing the same IRQ.

This change includs contributions from Tuan Phan <tphan@apm.com>.
Signed-off-by: NLoc Ho <lho@apm.com>
Acked-by: NBorislav Petkov <bp@suse.de>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/apei/ghes.c

@@ -1157,7 +1157,8 @@ static int ghes_probe(struct platform_device *ghes_dev)
 			       generic->header.source_id);
 			goto err_edac_unreg;
 		}
-		rc = request_irq(ghes->irq, ghes_irq_func, 0, "GHES IRQ", ghes);
+		rc = request_irq(ghes->irq, ghes_irq_func, IRQF_SHARED,
+				 "GHES IRQ", ghes);
 		if (rc) {
 			pr_err(GHES_PFX "Failed to register IRQ for generic hardware error source: %d\n",
 			       generic->header.source_id);