imx: imx8mq: handle ESDHC in mxc_get_clock

fsl_esdhc_imx driver will call "mxc_get_clock(MXC_ESDHC_CLK +
dev->seq)", however mxc_get_clock wrongly handle MXC_ESDHC_CLK
as root clk and cause sd card could not be detected in U-Boot proper,
as below:
"Loading Environment from MMC... unable to select a mode"

Handle MXC_ESDHC_CLK in mxc_get_clock to fix the issue.
Signed-off-by: NPeng Fan <peng.fan@nxp.com>
Tested-by: NBaruch Siach <baruch@tkos.co.il>
Tested-by: NFabio Estevam <festevam@gmail.com>

arch/arm/mach-imx/imx8m/clock_imx8mq.c

@@ -326,16 +326,20 @@ unsigned int mxc_get_clock(enum mxc_clock clk)
 {
 	u32 val;
 
-	if (clk == MXC_ARM_CLK)
+	switch(clk) {
+	case MXC_ARM_CLK:
 		return get_root_clk(ARM_A53_CLK_ROOT);
-
-	if (clk == MXC_IPG_CLK) {
+	case MXC_IPG_CLK:
 		clock_get_target_val(IPG_CLK_ROOT, &val);
 		val = val & 0x3;
 		return get_root_clk(AHB_CLK_ROOT) / (val + 1);
+	case MXC_ESDHC_CLK:
+		return get_root_clk(USDHC1_CLK_ROOT);
+	case MXC_ESDHC2_CLK:
+		return get_root_clk(USDHC2_CLK_ROOT);
+	default:
+		return get_root_clk(clk);
 	}
-
-	return get_root_clk(clk);
 }
 
 u32 imx_get_uartclk(void)