clk: baikal-t1: Mark Ethernet PLL as critical

We've discovered that disabling the so called Ethernet PLL causes reset of
the devices consuming its outgoing clock. The resets happen automatically
even if each underlying clock gate is turned off. Due to that we can't
disable the Ethernet PLL until the kernel is prepared for the corresponding
resets. So for now just mark the PLL clock provider as critical.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: linux-mips@vger.kernel.org
Link: https://lore.kernel.org/r/20200920110335.18034-1-Sergey.Semin@baikalelectronics.ru


Signed-off-by: Stephen Boyd <sboyd@kernel.org>