powerpc/hvc: Driver build breaks with !HVC_CONSOLE

Hi Stephen,

	next-20090925 randconfig build breaks on hvcs driver on powerpc,
with HVC_CONSOLE=n.

ERROR: ".hvc_put_chars" [drivers/char/hvcs.ko] undefined!
ERROR: ".hvc_get_chars" [drivers/char/hvcs.ko] undefined!

adding the dependency of HVC_CONSOLE helped

Signed-off-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>