clk: imx8mm: Mark dram_apb critical

This clock is used for dram operations inside TF-A and must be kept
enabled for features such as suspend/resume dram retention and busfreq
to work.

This is required for imx8mm suspend to work with NXP branch of TF-A.
There is an equivalent clk on imx8mq and it's always been marked as
critical in upstream.
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

drivers/clk/imx/clk-imx8mm.c

@@ -526,7 +526,7 @@ static int __init imx8mm_clocks_init(struct device_node *ccm_node)
 
 	/* IP */
 	clks[IMX8MM_CLK_DRAM_ALT] = imx8m_clk_composite("dram_alt", imx8mm_dram_alt_sels, base + 0xa000);
-	clks[IMX8MM_CLK_DRAM_APB] = imx8m_clk_composite("dram_apb", imx8mm_dram_apb_sels, base + 0xa080);
+	clks[IMX8MM_CLK_DRAM_APB] = imx8m_clk_composite_critical("dram_apb", imx8mm_dram_apb_sels, base + 0xa080);
 	clks[IMX8MM_CLK_VPU_G1] = imx8m_clk_composite("vpu_g1", imx8mm_vpu_g1_sels, base + 0xa100);
 	clks[IMX8MM_CLK_VPU_G2] = imx8m_clk_composite("vpu_g2", imx8mm_vpu_g2_sels, base + 0xa180);
 	clks[IMX8MM_CLK_DISP_DTRC] = imx8m_clk_composite("disp_dtrc", imx8mm_disp_dtrc_sels, base + 0xa200);