[PATCH] Make nvram_64.o a 64bit-only object

Make nvram_64.o dependent on 64bit, not on MULTIPLATFORM.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>