i2c: qcom-geni: Restore the source-clock selection policy

Currently, the source clock lookup prefers 32 MHz whenever that rate is
available, regardless of the rate configured by the platform. Before the
switch to looking up the clock index, the driver used the 32 MHz timing
table only if the current source clock rate was 32 MHz, and the 19.2 MHz
table otherwise.

On X1E80100 CRD, this results in switching the source clock from 19.2 MHz
to 32 MHz, which causes intermittent failures when probing the I2C HID
keyboard. These range from corrupted HID descriptors to failed resets
and transfer timeouts, which also affect the touchpad on the same bus.

Restore the original selection policy: use 32 MHz if already selected,
otherwise request 19.2 MHz. Look up the index for the selected rate and
keep the check that rejects higher-frequency multiples. This retains
the dynamic clock index lookup without preferring 32 MHz on platforms
that previously used 19.2 MHz. Report the requested rate if the lookup
fails.

Fixes: cb97bf3d4f91 ("i2c: qcom-geni: Fix hardcoded clock index in SE_GENI_CLK_SEL")
Assisted-by: LLM
Signed-off-by: Abel Vesa <abel.vesa@oss.qualcomm.com>
Tested-by: Hasty Heat <hastyheat@gmail.com>
Tested-by: Mitchell Augustin <mitchell.augustin@canonical.com>
Reviewed-by: Mitchell Augustin <mitchell.augustin@canonical.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://patch.msgid.link/20260928-b4-i2c-qcom-geni-preserve-source-clock-v1-1-9aded7552a76@oss.qualcomm.com

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