V4L/DVB (3745): Fix a bug at pluto2 Makefile

When pluto2 were selected, all other module dependencies were
just discarded.
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/dvb/pluto2/Makefile

-obj-$(CONFIG_DVB_PLUTO2) = pluto2.o
+obj-$(CONFIG_DVB_PLUTO2) += pluto2.o
 
 EXTRA_CFLAGS = -Idrivers/media/dvb/dvb-core/ -Idrivers/media/dvb/frontends/