various cleanups

c64/kernal/interrupts/ea81.return_from_interrupt.s

@@ -12,7 +12,7 @@ return_from_interrupt:
 	// Restore registers and return
 	// Sequence according to Compute's Mapping the 64 p73
 
-	_ply
-	_plx
+	ply_trash_a
+	plx_trash_a
 	pla
 	rti

c64/kernal/interrupts/fe47.default_nmi_handler.s

@@ -6,8 +6,8 @@ default_nmi_handler:
 
 	// Save registers, sequence according to Compute's Mapping the Commodore 64, page 73
 	pha
-	_phx
-	_phy
+	phx_trash_a
+	phy_trash_a
 
 	// XXX: RS-232 support is not implemented
 

c64/kernal/interrupts/hw_entry_irq.s

@@ -11,8 +11,8 @@ hw_entry_irq:
 
 	// Save registers, sequence according to Compute's Mapping the Commodore 64, page 73
 	pha
-	_phx
-	_phy
+	phx_trash_a
+	phy_trash_a
 
 #if CONFIG_CPU_MOS_6502 && CONFIG_BCD_SAFE_INTERRUPTS
 	cld // clear decimal flag to allow using it without disabling interrupts