fbdev: remove object duplication in Makefile

fbdev: remove object duplication in Makefile

The objects in $(fb-objs) $(fb-y) $(fb-m) are linked to fb.ko .

This line adds $(fb-y) to fb-objs, so the objects from $(fb-y) are
listed twice as the dependency of the module.

It works because Kbuild trims the duplicated objects from linking,
but there is no good reason to have this line.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200106081352.27730-1-masahiroy@kernel.org