ddr: imx8m: Fix the ddr init hang on imx8mq

On, i.MX8MQ, the PLL config must be done when ddrmix
isolation is released. So move the dram pll init after
iso config done. For other i.MX8M SOC, either init pll
before or after isolation is ok.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/drivers/ddr/imx/imx8m/ddr_init.c b/drivers/ddr/imx/imx8m/ddr_init.c
index 1296758..d6e915c 100644
--- a/drivers/ddr/imx/imx8m/ddr_init.c
+++ b/drivers/ddr/imx/imx8m/ddr_init.c
@@ -41,14 +41,14 @@
 	clock_set_target_val(DRAM_APB_CLK_ROOT, CLK_ROOT_ON | CLK_ROOT_SOURCE_SEL(4) |
 			     CLK_ROOT_PRE_DIV(CLK_ROOT_PRE_DIV4));
 
-	initial_drate = dram_timing->fsp_msg[0].drate;
-	/* default to the frequency point 0 clock */
-	ddrphy_init_set_dfi_clk(initial_drate);
-
 	/* disable iso */
 	reg32_write(0x303A00EC, 0x0000ffff); /* PGC_CPU_MAPPING */
 	reg32setbit(0x303A00F8, 5); /* PU_PGC_SW_PUP_REQ */
 
+	initial_drate = dram_timing->fsp_msg[0].drate;
+	/* default to the frequency point 0 clock */
+	ddrphy_init_set_dfi_clk(initial_drate);
+
 	/* D-aasert the presetn */
 	reg32_write(SRC_DDRC_RCR_ADDR, 0x8F000006);