CLOSE: send LISTEN, CLOSE, UNLISTEN to a serial device

close_iec sent its CLOSE command under ATN without first addressing the
device with LISTEN and without UNLISTEN after it, and built the command
with ORA $E0 (zero page) instead of ORA #$E0, so the byte it sent was
the secondary address ORed with whatever $E0 held. The drive never
learned of the CLOSE, so a file written on a channel was never written
to the disk.

The contract (Michael Steil, "Commodore Peripheral Bus: Part 2",
https://www.pagetable.com/?p=1031): CLOSE of a file on a serial device
sends LISTEN, then $E0 plus the secondary address, then UNLISTEN.
close_iec now does that, as iec_close_load already does for LOAD.

Not reported upstream (https://github.com/MEGA65/open-roms).

src/kernal/iec/close_iec.s

@@ -23,11 +23,17 @@ close_iec:
 	jsr iec_close_load 
 	jmp close_remove_from_table
 @1:
-	ora $E0 ; CLOSE command
+	; LISTEN, CLOSE, UNLISTEN - see https://www.pagetable.com/?p=1031
+	lda FAT, y
+	jsr LISTEN
+	bcs close_iec_end
+	lda SAT, y
+	ora #$E0 ; CLOSE command
 	sta TBTCNT
 	jsr iec_tx_command
 	bcs close_iec_end
 	jsr iec_tx_command_finalize
+	jsr UNLSN
 
 	; FALLTROUGH