clk: mpfs_clk: Enable DM_FLAG_PRE_RELOC flag

This driver is needed in the pre-relocation phase as the serial
driver depends on it.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Padmarao Begari <padmarao.begari@microchip.com>
Tested-by: Padmarao Begari <padmarao.begari@microchip.com>

drivers/clk/microchip/mpfs_clk.c

@@ -120,4 +120,5 @@ U_BOOT_DRIVER(mpfs_clk) = {
 	.ops = &mpfs_clk_ops,
 	.probe = mpfs_clk_probe,
 	.priv_auto = sizeof(struct clk),
+	.flags = DM_FLAG_PRE_RELOC,
 };