dm: Rename U_BOOT_DRIVER_ALIAS to DM_DRIVER_ALIAS

We use the U_BOOT_ prefix (i.e. U_BOOT_DRIVER) to declare a driver but
in every other case we just use DM_. Update the alias macros to use the
DM_ prefix.

We could perhaps rename U_BOOT_DRIVER() to DM_DRIVER(), but this macro
is widely used and there is at least some benefit to indicating it us a
U-Boot driver, particularly for code ported from Linux. So for now, let's
keep that name.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/gpio/sandbox.c b/drivers/gpio/sandbox.c
index f8fa4ba..dc8d506 100644
--- a/drivers/gpio/sandbox.c
+++ b/drivers/gpio/sandbox.c
@@ -327,7 +327,7 @@
 	ACPI_OPS_PTR(&gpio_sandbox_acpi_ops)
 };
 
-U_BOOT_DRIVER_ALIAS(sandbox_gpio, sandbox_gpio_alias)
+DM_DRIVER_ALIAS(sandbox_gpio, sandbox_gpio_alias)
 
 /* pincontrol: used only to check GPIO pin configuration (pinmux command) */