scsi: ufs: Delete is_init_prefetch from struct ufs_hba

Without variable is_init_prefetch, the current logic can guarantee
ufshcd_init_icc_levels() will execute only once, delete it now.

Link: https://lore.kernel.org/r/20200120130820.1737-7-huobean@gmail.com


Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Bean Huo <beanhuo@micron.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>