netdevsim: put netdevsim bus code into separate file

As the code related to netdevsim bus is going to get bigger, move the
existing code to a separate file.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/netdevsim/Makefile

@@ -3,7 +3,7 @@
 obj-$(CONFIG_NETDEVSIM) += netdevsim.o
 
 netdevsim-objs := \
-	netdev.o dev.o fib.o sdev.o
+	netdev.o dev.o fib.o sdev.o bus.o
 
 ifeq ($(CONFIG_BPF_SYSCALL),y)
 netdevsim-objs += \