scsi: isci: Remove unnecessary struct declaration

struct sci_phy_proto was already defined on line 142. The declaration here
is unnecessary. Remove it.

Link: https://lore.kernel.org/r/20210406105913.676746-1-wanjiabing@vivo.comSigned-off-by: Wan Jiabing <wanjiabing@vivo.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/isci/phy.h

@@ -447,7 +447,6 @@ void sci_phy_get_attached_sas_address(
 	struct isci_phy *iphy,
 	struct sci_sas_address *sas_address);
 
-struct sci_phy_proto;
 void sci_phy_get_protocols(
 	struct isci_phy *iphy,
 	struct sci_phy_proto *protocols);