powerpc/boot: Remove support for Marvell mv64x60 i2c controller

There are no longer any platforms that use Marvell's mv64x60's i2c
controller so remove its driver.

Signed-off-by: Mark Greer <mgreer@animalcreek.com>
Acked-by: Dale Farnsworth <dale@farnsworth.org>
Signed-off-by: Mark Greer &lt;<a href="mailto:mgreer@animalcreek.com">mgreer@animalcreek.com</a>&gt;<br>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>