clk: spacemit: k3: mark top_dclk as CLK_IS_CRITICAL

clk: spacemit: k3: mark top_dclk as CLK_IS_CRITICAL

top_dclk is the DDR bus clock. If it is gated by clk_disable_unused,
all memory-mapped bus transactions cease to function, causing DMA
engines to hang and general system instability.

Mark it CLK_IS_CRITICAL so the CCF never gates it during the
unused clock sweep.

Fixes: e371a77255b8 ("clk: spacemit: k3: add the clock tree")
Reviewed-by: Brian Masney <bmasney@redhat.com>
Signed-off-by: Troy Mitchell <troy.mitchell@linux.spacemit.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>