programmer: Smoothen register_par_master API

It was impossible to register a const struct par_master that would
point to dynamically allocated `data`. Fix that so that we won't
have to create more mutable globals.

Change-Id: I95bc92f6c54c5bcdac1c522ca87054aaffed0f40
Signed-off-by: Anastasia Klimchuk <aklm@chromium.org>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/54169
Original-Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/72201
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/gfxnvidia.c b/gfxnvidia.c
index faed11d..ec04a94 100644
--- a/gfxnvidia.c
+++ b/gfxnvidia.c
@@ -104,7 +104,7 @@
 
 	/* Write/erase doesn't work. */
 	programmer_may_write = false;
-	register_par_master(&par_master_gfxnvidia, BUS_PARALLEL);
+	register_par_master(&par_master_gfxnvidia, BUS_PARALLEL, NULL);
 
 	return 0;
 }