fbdev: aty: SPARC64 requires FB_ATY_CT

It looks like SPARC64 requires FB_ATY_CT to build without errors,
so have FB_ATY select FB_ATY_CT if both SPARC64 and PCI are enabled
instead of using "default y if SPARC64 && PCI", which is not strong
enough to prevent build errors.

As it currently is, FB_ATY_CT can be disabled, resulting in build
errors:

ERROR: modpost: "aty_postdividers" [drivers/video/fbdev/aty/atyfb.ko] undefined!
ERROR: modpost: "aty_ld_pll_ct" [drivers/video/fbdev/aty/atyfb.ko] undefined!

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Fixes: f7018c21 ("video: move fbdev to drivers/video/fbdev")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: sparclinux@vger.kernel.org
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-fbdev@vger.kernel.org
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: David Airlie <airlied@linux.ie>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20201127031752.10371-1-rdunlap@infradead.org