mmc: dt-bindings: Add resets/reset-names for Mediatek MMC bindings

Add description for resets/reset-names.

Cc: <stable@vger.kernel.org> # v5.4+
Fixes: 966580ad ("mmc: mediatek: add support for MT7622 SoC")
Signed-off-by: Wenbin Mei <wenbin.mei@mediatek.com>
Tested-by: Frank Wunderlich <frank-w@public-files.de>
Link: https://lore.kernel.org/r/20200814014346.6496-2-wenbin.mei@mediatek.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>