The SIMATIC IPC277E 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.

Tested on SIMATIC IPC277E.

Fixes: 648e9218 ("clk: x86: Stop marking clocks as CLK_IS_CRITICAL")
Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Cedric Hombourger <Cedric_Hombourger@mentor.com>
Signed-off-by: Srikanth Krishnakar <Srikanth_Krishnakar@mentor.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>