Fixes for MT011 in SD driver

Credit to Douglas Miller for these.

Source/HBIOS/sd.asm

@@ -233,6 +233,15 @@ RTCDEF		.SET	SD_OPRDEF	; SET DEFAULT IN HBIOS MAINLINE
 ; WIZNET W5500 AND IS NOT USED HERE.  CHANNEL 1 (CD0 & CS0) & 2 (CD1 & CS1)
 ; ARE ASSUMED TO BE CONNECTED TO SD CARDS.
 ;
+; NOTE THAT DOING AN "IN RDTR" WILL RETURN THE *EXISTING* CONTENTS
+; OF THE SHIFT REGISTER, THEN INITIATE AN SPI READ.  SO THE "IN" WILL BE
+; RETURNING THE DATA RECEIVED FROM THE PRIOR "IN RDTR", OR "OUT WRTR".
+; "IN RDNTR" WILL RETURN THE EXISTING SHIFT REGISTER CONTENTS WITHOUT
+; INITIATING A NEW SPI READ.
+;
+; THANKS TO DOUGLAS MILLER FOR BRINGING THIS BEHAVIOR TO MY ATTENTION
+; AND SUPPLYING ASSOCIATED FIXES.
+;
 SD_BASE		.EQU	$5C		; Module base address
 SD_DEVMAX	.EQU	2		; NUMBER OF PHYSICAL UNITS (SOCKETS)
 SD_WRTR		.EQU	SD_BASE + 0	; Write data and transfer
@@ -1428,6 +1437,10 @@ SD_EXECCMD1:
 ;
 	; GET RESULT
 	LD	E,0			; INIT TIMEOUT LOOP COUNTER
+#IF (SDMODE == SDMODE_MT)
+	CALL	SD_GET			; DISCARD STALE DATA FROM PUT
+#ENDIF
+;
 SD_EXECCMD2:
 	CALL	SD_GET			; GET A BYTE FROM THE CARD
 	OR	A			; SET FLAGS
@@ -1555,6 +1568,7 @@ SD_PUTDATA1:
 	OUT	(SD_WRTR),A		; SEND IT TWICE
 
 	LD	DE,$7FFF		; LOOP MAX (TIMEOUT)
+	IN	A,(SD_RDTR)		; DISCARD STALE DATA FROM OUT
 SD_PUTDATA2:
 	IN	A,(SD_RDTR)
 #ELSE
@@ -1604,6 +1618,9 @@ SD_PUTDATA3:
 ;
 SD_WAITRDY:
 	LD	DE,$FFFF		; LOOP MAX (TIMEOUT)
+#IF (SDMODE == SDMODE_MT)
+	CALL	SD_GET			; DISCARD STALE DATA - UNKNOWN CONTEXT
+#ENDIF
 SD_WAITRDY1:
 	CALL	SD_GET
 	INC	A			; $FF -> $00