renesas: reject PTP_STRICT_FLAGS as unsupported

The ravb_ptp_extts() function checks the flags coming from the
PTP_EXTTS_REQUEST ioctl, to ensure that future flags are not accepted on
accident.

This was updated to 'honor' the PTP_STRICT_FLAGS in commit 6138e687c7b6
("ptp: Introduce strict checking of external time stamp options.").
However, the driver does not *actually* validate the flags.

I originally fixed this driver to reject future flags in commit
592025a03b34 ("renesas: reject unsupported external timestamp flags"). It
is still unclear whether this hardware timestamps the rising, falling, or
both edges of the input signal.

Accepting requests with PTP_STRICT_FLAGS is a bug, as this could lead to
users mistakenly assuming a request with PTP_RISING_EDGE actually
timestamps the rising edge only.

Reject requests with PTP_STRICT_FLAGS (and hence all PTP_EXTTS_REQUEST2
requests) until someone with access to the datasheet or hardware knowledge
can confirm the timestamping behavior and update this driver.

Fixes: 6138e687c7b6 ("ptp: Introduce strict checking of external time stamp options.")
Signed-off-by: Jacob Keller <[email protected]>
Reviewed-by: Niklas Söderlund <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Link: https://patch.msgid.link/20250312-jk-net-fixes-supported-extts-flags-v2-2-ea930ba82459@intel.com
Signed-off-by: Paolo Abeni <[email protected]>

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