[SCSI] mpt2sas: fix infinite loop inside config request

This restriction is introduced just to avoid loop of
config_request. Retry must be limited so we have restricted
config request to maximum 2 times.

Signed-off-by: Kashyap Desai <kashyap.desai@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>