stmmac: Move the STMicroelectronics driver

Move the STMicroelectronics driver into driver/net/ethernet/stmicro/ and
make the necessary Kconfig and Makefile changes.

CC: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ethernet/Makefile b/drivers/net/ethernet/Makefile
index 26324a1..75d7a02 100644
--- a/drivers/net/ethernet/Makefile
+++ b/drivers/net/ethernet/Makefile
@@ -21,5 +21,6 @@
 obj-$(CONFIG_NET_VENDOR_RACAL) += racal/
 obj-$(CONFIG_SFC) += sfc/
 obj-$(CONFIG_NET_VENDOR_SMSC) += smsc/
+obj-$(CONFIG_NET_VENDOR_STMICRO) += stmicro/
 obj-$(CONFIG_NET_VENDOR_SUN) += sun/
 obj-$(CONFIG_NET_VENDOR_TEHUTI) += tehuti/