i3c: mipi-i3c-hci: Add HDR-DDR support

Add support for HDR-DDR private transfers.  Encode HDR-DDR Command
Descriptors and advertise HDR-DDR capability when supported by the
controller.

Carry the HDR Command Code in the descriptor CP, CMD and RNW fields.
Use the Immediate Data Transfer Command for writes of up to four bytes,
as is already done for SDR, and the Regular Data Transfer Command
otherwise.  The Immediate Data Transfer Command is write-only, which
suits HDR because the eighth bit of the HDR Command Code is field RNW,
so a write Command Code leaves that field zero as required.

Reject transfers shorter than one Data Word or with an odd byte count,
as HDR-DDR transfers are defined in whole Data Words and the I3C
specification requires at least one Data Word to follow the Command
Word.

Only advertise HDR-DDR capability when the driver can generate the
required descriptor format.

Assisted-by: GitHub-Copilot:claude-opus-5
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260920151248.46936-18-adrian.hunter@intel.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

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