mmc: renesas_sdhi: do hard reset if possible

All recent SDHI instances can be reset via the reset controller. If one
is found, use it instead of the open coded reset. This is to get a
future-proof sane reset state.

Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20210317091622.31890-4-wsa+renesas@sang-engineering.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>