net: mscc: Move miim commands into separate file.

Move miim functions that can be shared in a different file inside
mscc_eswitch.

Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
diff --git a/drivers/net/mscc_eswitch/Makefile b/drivers/net/mscc_eswitch/Makefile
index 32f411d..1ceb92a 100644
--- a/drivers/net/mscc_eswitch/Makefile
+++ b/drivers/net/mscc_eswitch/Makefile
@@ -1,2 +1,2 @@
 
-obj-$(CONFIG_MSCC_OCELOT_SWITCH) += ocelot_switch.o
+obj-$(CONFIG_MSCC_OCELOT_SWITCH) += ocelot_switch.o mscc_miim.o