net: ethernet: davinci_emac: Remove unnecessary #include

The '#include <mach/mux.h>' line in davinci_emac.c
causes a compile error because that header file
isn't found.  It turns out that the #include isn't
needed because the driver isn't (and shoudn't be)
touching the mux anyway, so remove it.

CC: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>