[POWERPC] celleb: fix scc_uhc.c dependency

scc_uhc.c depends on CONFIG_PCI, not CONFIG_USB. Because CONFIG_PCI
is always "y" on Celleb platform, we move scc_uhc.o to obj-y.

Signed-off-by: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>