firewire: ohci: optimize TSB41BA3D detection

Takes less source code and machine code, and less runtime with PHYs
other than TSB41BA3D (e.g. TSB81BA3 with device ID 0x831304 which takes
one instead of six read_paged_phy_reg now).
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

drivers/firewire/ohci.c

@@ -2159,38 +2159,26 @@ static int configure_1394a_enhancements(struct fw_ohci *ohci)
 	return 0;
 }
 
-#define TSB41BA3D_VID 0x00080028
-#define TSB41BA3D_PID 0x00833005
-
 static int probe_tsb41ba3d(struct fw_ohci *ohci)
 {
-	int reg, i, vendor_id, product_id;
+	/* TI vendor ID = 0x080028, TSB41BA3D product ID = 0x833005 (sic) */
+	static const u8 id[] = { 0x08, 0x00, 0x28, 0x83, 0x30, 0x05, };
+	int reg, i;
 
 	reg = read_phy_reg(ohci, 2);
 	if (reg < 0)
 		return reg;
+	if ((reg & PHY_EXTENDED_REGISTERS) != PHY_EXTENDED_REGISTERS)
+		return 0;
 
-	if ((reg & PHY_EXTENDED_REGISTERS) == PHY_EXTENDED_REGISTERS) {
-		vendor_id = 0;
-		for (i = 10; i < 13; i++) {
-			reg = read_paged_phy_reg(ohci, 1, i);
-			if (reg < 0)
-				return reg;
-			vendor_id = (vendor_id << 8) | reg;
-		}
-		product_id = 0;
-		for (i = 13; i < 16; i++) {
-			reg = read_paged_phy_reg(ohci, 1, i);
-			if (reg < 0)
-				return reg;
-			product_id = (product_id << 8) | reg;
-		}
-
-		if ((vendor_id == TSB41BA3D_VID) &&
-		    (product_id == TSB41BA3D_PID))
-			return 1;
+	for (i = ARRAY_SIZE(id) - 1; i >= 0; i--) {
+		reg = read_paged_phy_reg(ohci, 1, i + 10);
+		if (reg < 0)
+			return reg;
+		if (reg != id[i])
+			return 0;
 	}
-	return 0;
+	return 1;
 }
 
 static int ohci_enable(struct fw_card *card,