memory_mapped: Reduce `decode_sizes` to a single `max_rom_decode`

We used to store the maximum decode size, i.e. the maximum memory-mapped
range of the flash chip, per bus type (Parallel, LPC, FWH, SPI). There
was no programmer in the tree that really made use of it, though:
* The chipset drivers usually focus on a single bus type. And even if
  they advertise the whole default set (PAR, LPC, FWH), they only pro-
  vide a maximum decode size for one of them. The latter is probably
  wrong, should really more than one bus type be supported.
* PCI and external programmers all support only a single bus type, with
  the exception of `serprog` which doesn't set a maximum decode size.

What made the distinction even less useful is that for some chips that
support multiple bus types, i.e. LPC+FWH, we can't even detect which
type it is. The existing code around this also only tried to provide
the best possible warning message at the expense of breaking the pro-
grammer abstraction.

Hence, unify the set of sizes into a single `max_rom_decode` property.
We store it inside the `registered_master` struct right away, to avoid
any more use of globals.

Change-Id: I2aaea18d5b4255eb843a625b016ee74bb145ed85
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.sourcearcade.org/c/flashprog/+/72531
diff --git a/sb600spi.c b/sb600spi.c
index ba7bd3e..41496a5 100644
--- a/sb600spi.c
+++ b/sb600spi.c
@@ -652,8 +652,8 @@
 
 	/* Starting with Yangtze the SPI controller got a different interface with a much bigger buffer. */
 	if (amd_gen < CHIPSET_YANGTZE)
-		register_spi_master(&spi_master_sb600, NULL);
+		register_spi_master(&spi_master_sb600, 0, NULL);
 	else
-		register_spi_master(&spi_master_yangtze, NULL);
+		register_spi_master(&spi_master_yangtze, 0, NULL);
 	return 0;
 }