USB: ehci-fsl: Turn on cache snooping on MPC8xxx

If a MPC8xxx was being used, 'have_sysif_regs' should be set and
it should setup cache snooping for all the 4GB space on both PPC32
and PPC64.

Signed-off-by: Pan Jiafei <Jiafei.Pan@freescale.com>
Acked-by: Li Yang <leoli@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>