[POWERPC] Remove todc code from ARCH=powerpc

Apparently we've copied the todc drivers, for various RTCs used in
embedded machines from ARCH=ppc to ARCH=powerpc, despite the fact that
it's never used in the latter.  This patch removes it.

If we ever need these drivers (which we probably shouldn't now the RTC
class stuff is in), we can transfer them one by one from ARCH=ppc,
removing from the hideous abomination which is the todc
"infrastructure".

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>