pinctrl: th1520: Mark driver as DM_FLAG_PRE_RELOC

It's common that UARTs are bound and probed before U-Boot relocation, in
which case the UART's pincontroller and pinconfig must be probed first.
Let's apply DM_FLAG_PRE_RELOC to the driver, allow it to bind before
relocation.

Signed-off-by: Yao Zi <ziyao@disroot.org>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>

drivers/pinctrl/pinctrl-th1520.c

@@ -697,4 +697,5 @@ U_BOOT_DRIVER(th1520_pinctrl) = {
 	.probe = th1520_pinctrl_probe,
 	.priv_auto = sizeof(struct th1520_pinctrl),
 	.ops = &th1520_pinctrl_ops,
+	.flags = DM_FLAG_PRE_RELOC,
 };