Merge branch 'dsa-headers-cleanup'

Vivien Didelot says:

====================
net: dsa: headers cleanup

The DSA core files share a common private header file. Include the DSA
public header there instead of independently in each core source file.

DSA core and its drivers use switchdev, thus include switchdev.h in the
public DSA header. This allows us to get rid of the forward declaration
and use typedef defined by switchdev.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>