acpi/nfit: Fix user-initiated ARS to be "ARS-long" rather than "ARS-short"

A "short" ARS (address range scrub) instructs the platform firmware to
return known errors. In contrast, a "long" ARS instructs platform
firmware to arrange every data address on the DIMM to be read / checked
for poisoned data.

The conversion of the flags in commit d3abaf43 "acpi, nfit: Fix
Address Range Scrub completion tracking", changed the meaning of passing
'0' to acpi_nfit_ars_rescan(). Previously '0' meant "not short", now '0'
is ARS_REQ_SHORT. Pass ARS_REQ_LONG to restore the expected scrub-type
behavior of user-initiated ARS sessions.

Fixes: d3abaf43 ("acpi, nfit: Fix Address Range Scrub completion tracking")
Reported-by: Jacek Zloch <jacek.zloch@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>