ppc/pnv: Move PNOR to offset 0 in the ISA FW space

skiboot has a bug that does not handle ISA FW access correctly for IDSEL
devices > 0, and the current PNOR default address and size puts 64MB in
device 0 and 64MB in device 1, which causes skiboot to hit this bug and
breaks PNOR accesses.

Move the PNOR address down to 0 for now, so a 256MB PNOR can be accessed
via device 0.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>

include/hw/ppc/pnv_pnor.h

@@ -13,9 +13,11 @@
 #include "hw/sysbus.h"
 
 /*
- * PNOR offset on the LPC FW address space
+ * PNOR offset on the LPC FW address space. For now this should be 0 because
+ * skiboot 7.1 has a bug where IDSEL > 0 (LPC FW address > 256MB) access is
+ * not performed correctly.
  */
-#define PNOR_SPI_OFFSET         0x0c000000UL
+#define PNOR_SPI_OFFSET         0x00000000UL
 
 #define TYPE_PNV_PNOR  "pnv-pnor"
 OBJECT_DECLARE_SIMPLE_TYPE(PnvPnor, PNV_PNOR)