USB: host: Remove ehci-octeon and ohci-octeon drivers

Remove special-purpose octeon drivers and instead use ehci-platform
and ohci-platform as suggested with
http://marc.info/?l=linux-mips&m=140139694721623&w=2

[andreas.herrmann:
    fixed compile error]

Cc: David Daney <david.daney@cavium.com>
Cc: Alex Smith <alex.smith@imgtec.com>
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Andreas Herrmann <andreas.herrmann@caviumnetworks.com>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>