isci: fix a build warning

Use min_t to address:
drivers/scsi/isci/probe_roms.c: In function ‘isci_get_efi_var’:
drivers/scsi/isci/probe_roms.c:241: warning: comparison of distinct pointer types lacks a cast
Reported-by: NDavid Milburn <dmilburn@redhat.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

drivers/scsi/isci/probe_roms.c

@@ -250,9 +250,8 @@ struct isci_orom *isci_get_efi_var(struct pci_dev *pdev)
 		return NULL;
 	}
 
-	copy_len = min(evar->DataSize,
-		       min(oem_hdr->len - sizeof(*oem_hdr),
-			   sizeof(*rom)));
+	copy_len = min_t(u16, evar->DataSize,
+			 min_t(u16, oem_hdr->len - sizeof(*oem_hdr), sizeof(*rom)));
 
 	memcpy(rom, (char *)evar->Data + sizeof(*oem_hdr), copy_len);