openpower: Default PNOR_SQUASHFS to n

Witherspoon is the only system that uses this option. Instead of
updating all of the non-Witherspoon systems to turn it off, this commit
defaults it to 'n' and updates the witherspoon defconfigs to enable it.

The change to zz is due to the new default.

Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/openpower/package/openpower-pnor/Config.in b/openpower/package/openpower-pnor/Config.in
index 92adf36..a673e2b 100644
--- a/openpower/package/openpower-pnor/Config.in
+++ b/openpower/package/openpower-pnor/Config.in
@@ -160,6 +160,6 @@
 
 config BR2_BUILD_PNOR_SQUASHFS
         bool "Create a virtual PNOR image along with the standard image"
-        default y
+        default n
 
 endmenu