mmc: sdhci-xenon: add timeout for PHY init complete

AC5X spec says PHY init complete bit must be polled until zero.
We see cases in which timeout can take longer than the standard
calculation on AC5X, which is expected following the spec comment above.
According to the spec, we must wait as long as it takes for that bit to
toggle on AC5X.
Cap that with 100 delay loops so we won't get stuck forever.

Fixes: 06c8b667

 ("mmc: sdhci-xenon: Add support to PHYs of Marvell Xenon SDHC")
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Elad Nachman <enachman@marvell.com>
Link: https://lore.kernel.org/r/20240222191714.1216470-3-enachman@marvell.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>