Add a variant op to allow host drivers to initialize nonstandard
crypto-related fields in the PRDT.  This is needed to support inline
encryption on the "Exynos" UFS controller.

Note that this will be used together with the support for overriding the
PRDT entry size that was already added by commit ada1e653 ("scsi: ufs:
core: Allow UFS host drivers to override the sg entry size").
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Peter Griffin <peter.griffin@linaro.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20240708235330.103590-5-ebiggers@kernel.orgReviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>