clk: mediatek: Fix MT2701 dependencies

If I say "no" to "Clock driver for Mediatek MT2701", I don't want to
be asked individually about each sub-driver. No means no.

Additionally, this driver shouldn't be proposed at all on non-mediatek
builds, unless build-testing.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Fixes: e9862118

 ("clk: mediatek: Add MT2701 clock support")
Reviewed-by: Andreas Färber <afaerber@suse.de>
Reviewed-by: James Liao <jamesjj.liao@mediatek.com>
Cc: Shunli Wang <shunli.wang@mediatek.com>
Cc: Erin Lo <erin.lo@mediatek.com>
Cc: Michael Turquette <mturquette@baylibre.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>