mmc: sdhci-esdhc-imx: correct the tuning start tap and step setting

mmc: sdhci-esdhc-imx: correct the tuning start tap and step setting

Current code logic may be impacted by the setting of ROM/Bootloader,
so unmask these bits first, then setting these bits accordingly.

Fixes: 2b16cf326b70 ("mmc: sdhci-esdhc-imx: move tuning static configuration into hwinit function")
Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20221207112315.1812222-1-haibo.chen@nxp.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>