memory_bus: Turn flashbase into a par_master member `rom_base`

Get rid of the global `flashbase`. Treat overrides for the `rom_base`
similar to `max_rom_decode`: Gather the information in `internal_data`
and then pass it to register_par_master().

Change-Id: Ib9ed7234a849fe3550200fd602226d0036da15f0
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.sourcearcade.org/c/flashprog/+/436
diff --git a/atahpt.c b/atahpt.c
index beaa52d..05b11e9 100644
--- a/atahpt.c
+++ b/atahpt.c
@@ -74,7 +74,7 @@
 	reg32 |= (1 << 24);
 	rpci_write_long(dev, REG_FLASH_ACCESS, reg32);
 
-	return register_par_master(&par_master_atahpt, BUS_PARALLEL, 0, NULL);
+	return register_par_master(&par_master_atahpt, BUS_PARALLEL, 0, 0, NULL);
 }
 
 static void atahpt_chip_writeb(const struct flashctx *flash, uint8_t val,