gpio: omap_gpio: Add DM_FLAG_PRE_RELOC flag

With DM enabled in SPL, DM_FLAG_PRE_RELOC is required for
the omap_gpio driver to be bound to the gpio devices.

Therefore, add DM_FLAG_PRE_RELOC flag to the omap_gpio driver.

Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

drivers/gpio/omap_gpio.c

@@ -345,6 +345,7 @@ U_BOOT_DRIVER(gpio_omap) = {
 	.bind	= omap_gpio_bind,
 	.probe	= omap_gpio_probe,
 	.priv_auto_alloc_size = sizeof(struct gpio_bank),
+	.flags = DM_FLAG_PRE_RELOC,
 };
 
 #endif /* CONFIG_DM_GPIO */