net: mscc: ocelot: fix duplicate driver name error

When compiling a kernel which has both CONFIG_NET_DSA_MSCC_OCELOT_EXT
and CONFIG_MSCC_OCELOT_SWITCH enabled, the following error message will
be printed:

[    5.266588] Error: Driver 'ocelot-switch' is already registered, aborting...

Rename the ocelot_ext.c driver to "ocelot-ext-switch" to avoid the name
duplication, and update the mfd_cell entry for its resources.

Fixes: 3d7316ac

 ("net: dsa: ocelot: add external ocelot switch control")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>