ARM: ep93xx: multiplatform support

With the clock support and the interrupts out of the way, ep93xx can be
compiled into the same kernel image as the other ARMv4/v5 platforms. The
last obstacle are the two workarounds for broken boot loaders that
require us to re-initialize the ethernet controller and/or the watchdog
on certain machines.

Move this code into the decompressor sources directly, checking for
each possibly affected machine individually.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>