scsi: ufs-qcom: Make structure ufs_hba_qcom_vops constant

Static structure ufs_hba_qcom_vops, of type ufs_hba_variant_ops, is used
only once, when it is passed as the second argument to function
ufshcd_pltfrm_init(). In the definition of ufshcd_pltfrm_init(), its second
parameter (corresponding to ufs_hba_qcom_vops) is declared as
constant. Hence declare ufs_hba_qcom_vops itself constant as well to
protect it from unintended modification.  Issue found with Coccinelle.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Reviewed-by: Vivek Gautam <vivek.gautam@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>