clk: microchip: mpfs: mark CLK_ATHENA as critical

CLK_ATHENA is another fabric interconnect and should be marked as critical
as with FIC0-3, since disabling it will cause part of the fabric to go
into reset.

Fixes: 635e5e73

 ("clk: microchip: Add driver for Microchip PolarFire SoC")
Reviewed-by: Daire McNamara <daire.mcnamara@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20220413075835.3354193-3-conor.dooley@microchip.com
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>