mmc: sdhci-esdhc-imx: clear the buffer_read_ready to reset standard tuning circuit

To reset standard tuning circuit completely, after clear ESDHC_MIX_CTRL_EXE_TUNE,
also need to clear bit buffer_read_ready, this operation will finally clear the
USDHC IP internal logic flag execute_tuning_with_clr_buf, make sure the following
normal data transfer will not be impacted by standard tuning logic used before.

Find this issue when do quick SD card insert/remove stress test. During standard
tuning prodedure, if remove SD card, USDHC standard tuning logic can't clear the
internal flag execute_tuning_with_clr_buf. Next time when insert SD card, all
data related commands can't get any data related interrupts, include data transfer
complete interrupt, data timeout interrupt, data CRC interrupt, data end bit interrupt.
Always trigger software timeout issue. Even reset the USDHC through bits in register
SYS_CTRL (0x2C, bit28 reset tuning, bit26 reset data, bit 25 reset command, bit 24
reset all) can't recover this. From the user's point of view, USDHC stuck, SD can't
be recognized any more.

Fixes: d9370424c948 ("mmc: sdhci-esdhc-imx: reset tuning circuit when power on mmc card")
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/1634263236-6111-1-git-send-email-haibo.chen@nxp.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

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