[POWERPC] Export DCR symbols for modules

In order to compile drivers as modules that uses some of the
DCR functions, we need to export the symbols.  Example, EMAC
driver and other drivers that are under development use these
functions.

Signed-off-by: Murali Iyer <mniyer@us.ibm.com>
Acked-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>