powerpc: undeprecate the old OF device tree accessors for now

The recent addition of __deprecated to the declarations for
find_devices etc. produces a whole pile of warnings from the
ppc32 code.  Since those functions still work perfectly well on
ppc32, which doesn't have hotplug support for anything in the
OF device tree, and we don't have time to fix that code now,
remove the __deprecated markings for now.

Signed-off-by: Paul Mackerras <paulus@samba.org>