Generalize the new mux_cfg code to support interrupt and
EDMA event muxing on dm355.  Move the MMC0 event mux logic
to the device setup code, away from clock enable code where
it doesn't belong.  Mux the EDMA error interrupts.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>