acpi, nfit: Collect shutdown status

Some NVDIMMs, in addition to providing an indication of whether the
previous shutdown was clean, also provide a running count of lifetime
dirty-shutdown events for the device. In anticipation of this
functionality appearing on more devices arrange for the nfit driver to
retrieve / cache this data at DIMM discovery time, and export it via
sysfs.

Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/acpi/nfit/nfit.h

@@ -162,6 +162,8 @@ struct nfit_memdev {
 enum nfit_mem_flags {
 	NFIT_MEM_LSR,
 	NFIT_MEM_LSW,
+	NFIT_MEM_DIRTY,
+	NFIT_MEM_DIRTY_COUNT,
 };
 
 /* assembled tables for a given dimm/memory-device */
@@ -184,6 +186,7 @@ struct nfit_mem {
 	struct resource *flush_wpq;
 	unsigned long dsm_mask;
 	unsigned long flags;
+	u32 dirty_shutdown;
 	int family;
 };