scsi: ufs: ufshpb: Change sysfs node hpb_stats/rb_* prefix to start with rcmd_*

scsi: ufs: ufshpb: Change sysfs node hpb_stats/rb_* prefix to start with rcmd_*

According to the documentation of the sysfs nodes rb_noti_cnt,
rb_active_cnt and rb_inactive_cnt, these are all related to HPB
recommendation in UPIU response packet. 'rcmd' (recommendation) should be
the correct abbreviation.

Change the sysfs documentation about these sysfs nodes to highlight what
they mean under different HPB control modes.

Link: https://lore.kernel.org/r/20220505134707.35929-5-huobean@gmail.com
Reviewed-by: Keoseong Park <keosung.park@samsung.com>
Signed-off-by: Bean Huo <beanhuo@micron.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>