Move the definition of this data structure since it is only used in a
single source file.

Link: https://lore.kernel.org/r/20220419225811.4127248-28-bvanassche@acm.orgTested-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Reviewed-by: Bean Huo <beanhuo@micron.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>