Update md.asm

Simplify stack setup for relocatable code

Source/HBIOS/md.asm

@@ -813,13 +813,10 @@ MD_FNCALL:
 	CALL	PRTHEXWORD
 #ENDIF
 ;
-	LD	HL,MD_FNRET		; ADDRESS RELOCATABLE CODE TO RETURN TO
 	HB_DI
 	LD	(FF_SAVSTK),SP		; SAVE CURRENT STACK
-	LD	SP,HBX_BUF_END-2	; SETUP A NEW HIMEM STACK AT END OF HX_BUF
-	EX	(SP),HL			; BEHIND CODE WITH RETURN ADDRESS PREPOPULATED
-	JP	HBX_BUF			; EXECUTE RELOCATED CODE
-MD_FNRET:
+	LD	SP,HBX_BUF_END		; SETUP A NEW HIMEM STACK AT END OF HX_BUF
+	CALL	HBX_BUF			; EXECUTE RELOCATED CODE
 	LD	SP,(FF_SAVSTK)		; RESTORE STACK
 	HB_EI
 ;