Currently, tmio_mmc_ops is static data and tmio_mmc_host_probe()
updates some hooks in the static data.  This is a problem when
two or more instances call tmio_mmc_host_probe() and each of them
requests to use its own card_busy/start_signal_voltage_switch.

We can borrow a solution from sdhci_alloc_host().  Copy the whole
ops structure to host->mmc_host_ops, then override the hooks in
malloc'ed data.  Constify tmio_mmc_ops since it is now a template
ops used by default.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>