dm: core: Enable SPL_SIMPLE_BUS by default

This option is needed for all SoCs which have nodes on bus. Without
enabling this drivers are not found and probed.
Issue was found on Zynq MMC probe.
Enable this option by default.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/core/Kconfig

@@ -134,7 +134,7 @@ config SIMPLE_BUS
 config SPL_SIMPLE_BUS
 	bool "Support simple-bus driver in SPL"
 	depends on SPL_DM && SPL_OF_CONTROL
-	default n
+	default y
 	help
 	  Supports the 'simple-bus' driver, which is used on some systems
 	  in SPL.