MAINTAINERS: merge entries for felix and ocelot drivers

MAINTAINERS: merge entries for felix and ocelot drivers

The ocelot switchdev driver also provides a set of library functions for
the felix DSA driver, which in practice means that most of the patches
will be of interest to both groups of driver maintainers.

So, as also suggested in the discussion here, let's merge the 2 entries
into a single larger one:
https://www.spinics.net/lists/netdev/msg657412.html

Note that the entry has been renamed into "OCELOT SWITCH" since neither
Vitesse nor Microsemi exist any longer as company names, instead they
are now named Microchip (which again might be subject to change in the
future), so use the device family name instead.

Suggested-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>