cleanup in multiprotocol IEC support

src/kernal/iec/iec_rx_byte.s

@@ -17,7 +17,7 @@
 iec_rx_dispatch:
 
 	lda IECPROTO
-	cmp #$01
+	cmp #IEC_JIFFY
 	beq_16 jiffydos_rx_byte
 
 	// FALLTROUGH
@@ -54,7 +54,7 @@ iec_rx_byte:
 
 	// Check if DolphinDOS was detected
 	lda IECPROTO
-	cmp #$02
+	cmp #IEC_DOLPHIN
 	bne iec_rx_no_dolphindos
 
 	// For DolphinDOS just fetch the byte from parallel port

src/kernal/iec/iec_tx_byte.s

@@ -19,7 +19,7 @@ iec_tx_dispatch:
 
 	php                                // preserve C flag for EOI indication
 	lda IECPROTO
-	cmp #$01
+	cmp #IEC_JIFFY
 	bne !+
 
 	plp
@@ -71,7 +71,7 @@ iec_tx_common:
 
 	// Check if DolphinDOS was detected
 	lda IECPROTO
-	cmp #$02
+	cmp #IEC_DOLPHIN
 	bne iec_tx_no_dolphindos
 
 	// For DolphinDOS just push the byte to parallel port (set it to output first)

src/kernal/iec/load_iec.s

@@ -107,12 +107,12 @@ load_iec:
 	lda IECPROTO
 
 #if CONFIG_IEC_JIFFYDOS
-	cmp #$01
+	cmp #IEC_JIFFY
 	beq_16 jiffydos_load               // branch if JiffyDOS
 #endif
 
 #if CONFIG_IEC_DOLPHINDOS
-	cmp #$02
+	cmp #IEC_DOLPHIN
 	beq_16 dolphindos_load             // branch if DolphinDOS
 #endif