platform/x86: pmc_atom: Add Siemens CONNECT X300 to critclk_systems DMI table

The CONNECT X300 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 CONNECT X300.

Fixes: 648e9218 ("clk: x86: Stop marking clocks as CLK_IS_CRITICAL")
Signed-off-by: Michael Haener <michael.haener@siemens.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>