drm/radeon: init atpx at switcheroo register time v2

If we do it at enable time, it's too late for the feature
checks.

v2: drop .init setting as per Peter's comments

bug: https://bugzilla.kernel.org/show_bug.cgi?id=115321
Reviewed-by: Peter Wu <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>
Cc: Peter Wu <[e-mail]>

drivers/gpu/drm/radeon/radeon_atpx_handler.c

···
 static const struct vga_switcheroo_handler radeon_atpx_handler = {
 	.switchto = radeon_atpx_switchto,
 	.power_state = radeon_atpx_power_state,
-	.init = radeon_atpx_init,
 	.get_client_id = radeon_atpx_get_client_id,
 };
 
···
 		printk(KERN_INFO "vga_switcheroo: detected switching method %s handle\n",
 		       acpi_method_name);
 		radeon_atpx_priv.atpx_detected = true;
+		radeon_atpx_init();
 		return true;
 	}
 	return false;