ACPI: APEI: Use ERST timeout for slow devices

Slow devices such as flash may not meet the default 1ms timeout value,
so use the ERST max execution time value that they provide as the
timeout if it is larger.

Signed-off-by: Jeshua Smith <jeshuas@nvidia.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>