thermal/drivers/mediatek: Fix bank number settings on mt8183

MT8183_NUM_ZONES should be set to 1
because MT8183 doesn't have multiple banks.

Fixes: a4ffe6b5 ("thermal: mediatek: add support for MT8183")
Signed-off-by: Michael Kao <michael.kao@mediatek.com>
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200323121537.22697-6-michael.kao@mediatek.com