AMD sb800 sb900: Fix corruption of a global ramstage variable

A late for loop may reference over the current array allocation
and corrupt an unrelated global variable. As a quick fix bumb the
size of the array allocation uniformly to 6.

Change-Id: Ib067fdf077e091d13e32cc3a8e4a0b713d19bcc2
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/3914
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@google.com>
Reviewed-by: Bruce Griffith <Bruce.Griffith@se-eng.com>

src/mainboard/advansus/a785e-i/mptable.c

@@ -28,7 +28,7 @@
 
 extern int bus_isa;
 extern u8 bus_rs780[11];
-extern u8 bus_sb800[2];
+extern u8 bus_sb800[6];
 extern u32 apicid_sb800;
 extern u32 bus_type[256];
 extern u32 sbdn_rs780;