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/Kconfig b/drivers/net/ethernet/Kconfig
index 8375b8b..c38e902 100644
--- a/drivers/net/ethernet/Kconfig
+++ b/drivers/net/ethernet/Kconfig
@@ -30,6 +30,7 @@
 source "drivers/net/ethernet/racal/Kconfig"
 source "drivers/net/ethernet/sfc/Kconfig"
 source "drivers/net/ethernet/smsc/Kconfig"
+source "drivers/net/ethernet/stmicro/Kconfig"
 source "drivers/net/ethernet/sun/Kconfig"
 source "drivers/net/ethernet/tehuti/Kconfig"