The SIMATIC IPC227E uses the PMC clock for on-board components and gets
stuck during boot if the clock is disabled. Therefore, add this device
to the critical systems list.

Fixes: 648e9218 ("clk: x86: Stop marking clocks as CLK_IS_CRITICAL")
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>