Initially, the TMU_ROOT clock was marked as critical, which automatically
made the AHB clock to stay always on. Since the TMU_ROOT clock is not
marked as critical anymore, following commit:

"clk: imx8mq: Remove CLK_IS_CRITICAL flag for IMX8MQ_CLK_TMU_ROOT"

all the clocks that derive from ipg_root clock (and implicitly ahb clock)
would also have to enable, along with their own gate, the AHB clock.

But considering that AHB is actually a bus that has to be always on, we mark
it as critical in the clock provider driver and then all the clocks that
derive from it can be controlled through the dedicated per IP gate which
follows after the ipg_root clock.
Signed-off-by: Abel Vesa <abel.vesa@nxp.com>
Tested-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>