mmc: sdhci-of-dwcmshc: factor out code into dwcmshc_rk35xx_init

mmc: sdhci-of-dwcmshc: factor out code into dwcmshc_rk35xx_init

Continue factor out code fron probe into dwcmshc_rk35xx_init.

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/4f1f2fa403ce7f0b4d79afb7d7e8a1690cde5d6c.1722847198.git.unicorn_wang@outlook.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>