clk: imx8m: Set CLK_GET_RATE_NOCACHE on dram clocks

These clocks are only modified as part of DRAM frequency switches during
which DRAM itself is briefly inaccessible. The switch is performed with
a SMC call to by TF-A which runs from a SRAM area; upon returning to
linux several clocks bits are modified and we need to update them.

For rate bits an easy solution is to just mark with
CLK_GET_RATE_NOCACHE so that new rates are always read back from
registers.

Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Reviewed-by: Abel Vesa <abel.vesa@nxp.com>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>