mmc: sdhci-of-dwcmshc: move two rk35xx functions

mmc: sdhci-of-dwcmshc: move two rk35xx functions

This patch just move dwcmshc_rk35xx_init() and
dwcmshc_rk35xx_postinit() to put the functions
of rk35xx together as much as possible.

This change is an intermediate process before
further modification.

Signed-off-by: Chen Wang <unicorn_wang@outlook.com>
Tested-by: Drew Fustini <drew@pdp7.com> # TH1520
Tested-by: Inochi Amaoto <inochiama@outlook.com> # Duo and Huashan Pi
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/54204702d5febd3e867eb3544c36919fe4140a88.1722847198.git.unicorn_wang@outlook.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>