programmer: Move .max_rom_decode into struct master_common

This is useful information from a chipdriver perspective. It also saves
us the open-coded tracking of the "registered master" in `cli_classic.c`
right away.

Change-Id: I532e9b1802184520852fe0b45650239ea252a60d
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.sourcearcade.org/c/flashprog/+/430
diff --git a/parallel.c b/parallel.c
index 5746862..3e32d59 100644
--- a/parallel.c
+++ b/parallel.c
@@ -84,13 +84,15 @@
 		return ERROR_FLASHPROG_BUG;
 	}
 
-	if (max_rom_decode)
-		rmst.max_rom_decode = max_rom_decode;
-	else
-		rmst.max_rom_decode = DEFAULT_MAX_DECODE_PARALLEL;
 	rmst.buses_supported = buses;
 	rmst.par = *mst;
 	if (data)
 		rmst.par.data = data;
+
+	if (max_rom_decode)
+		rmst.common.max_rom_decode = max_rom_decode;
+	else
+		rmst.common.max_rom_decode = DEFAULT_MAX_DECODE_PARALLEL;
+
 	return register_master(&rmst);
 }