ACPI: APEI: ERST: remove unneeded semicolon

Eliminate the following coccicheck warning:
./drivers/acpi/apei/erst.c:691:2-3: Unneeded semicolon

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>