ppc4xx: Consolidate PPC4xx UIC defines

This 2nd patch now removes all UIC mask bit definition. They should be
generated from the vectors by using the UIC_MASK() macro from now on.
This way only the vectors need to get defined for new PPC's.

Also only the really used interrupt vectors are now defined. This makes
definitions for new PPC versions easier and less error prone.

Another part of this patch is that the 4xx emac driver got a little
cleanup, since now the usage of the interrupts is clearer.

Signed-off-by: Stefan Roese <sr@denx.de>