[SCSI] mpt3sas: remove unused variables

The variable 'chain_flags' and 'phy_number' are initialized but never used
otherwise, So remove those unused variables.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Sreekanth Reddy <Sreekanth.Reddy@lsi.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>