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: NJacky Bai <ping.bai@nxp.com>
Signed-off-by: NPeng Fan <peng.fan@nxp.com>

drivers/ddr/imx/imx8m/ddr_init.c

@@ -41,14 +41,14 @@ void ddr_init(struct dram_timing_info *dram_timing)
 	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);