Use correct access permissions during ROM decompression

If HAL+OS are contiguous, the combined image is initially mapped as
OSAP_None in order to allow for decompression. Fix the discontiguous
case to use the same permissions

s/HAL

@@ -746,7 +746,7 @@ RISCOS_Start
         SUB     a4, v7, v5
         LDR     a3, [v5, #OSHdr_DecompressHdr]
         CMP     a3, #0
-        MOVNE   a3, #0
+        MOVNE   a3, #OSAP_None
         MOVEQ   a3, #OSAP_ROM
         BL      Init_MapIn
         MOV     a3, v5