scsi: ufs: Make ufshcd_add_command_trace() easier to read

scsi: ufs: Make ufshcd_add_command_trace() easier to read

Since the lrbp->cmd expression occurs multiple times, introduce a new local
variable to hold that pointer. This patch does not change any
functionality.

Cc: Bean Huo <beanhuo@micron.com>
Cc: Can Guo <cang@codeaurora.org>
Cc: Avri Altman <avri.altman@wdc.com>
Cc: Stanley Chu <stanley.chu@mediatek.com>
Cc: Tomas Winkler <tomas.winkler@intel.com>
Link: https://lore.kernel.org/r/20191224220248.30138-3-bvanassche@acm.org
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Reviewed-by: Can Guo <cang@codeaurora.org>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>