Bitbanging MDIO driver for DM framework.

Linux DTS compatible MDIO bitbanging driver.
Both clause 22 and clause 45 MDIO supported and validated.

Heavily based on the Linux drivers (more or less the same code base).

Signed-off-by: Markus Gothe <markus.gothe@genexis.eu>
diff --git a/drivers/net/Makefile b/drivers/net/Makefile
index f5ab1f5..e51a917 100644
--- a/drivers/net/Makefile
+++ b/drivers/net/Makefile
@@ -61,6 +61,7 @@
 obj-$(CONFIG_MACB) += macb.o
 obj-$(CONFIG_MCFFEC) += mcffec.o mcfmii.o
 obj-$(CONFIG_MDIO_IPQ4019) += mdio-ipq4019.o
+obj-$(CONFIG_MDIO_GPIO_BITBANG) += mdio_gpio.o
 obj-$(CONFIG_MDIO_MUX_I2CREG) += mdio_mux_i2creg.o
 obj-$(CONFIG_MDIO_MUX_MESON_G12A) += mdio_mux_meson_g12a.o
 obj-$(CONFIG_MDIO_MUX_MESON_GXL) += mdio_mux_meson_gxl.o