staging/octeon: Allow test build on !MIPS

Add compile test support by moving all includes of files under
asm/octeon into octeon-ethernet.h, and if we're not on MIPS,
stub out all the calls into the octeon support code in octeon-stubs.h

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>