openpower: pnor: Fix BR2_TARGET_SKIBOOT_XZ option

op-build/openpower/package/openpower-pnor/Config.in:82: syntax error
op-build/openpower/package/openpower-pnor/Config.in:81: unknown option "boolean"

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 a673e2b..2fe0b9d 100644
--- a/openpower/package/openpower-pnor/Config.in
+++ b/openpower/package/openpower-pnor/Config.in
@@ -78,7 +78,7 @@
             String used to define skiboot lid filename
 
 config BR2_TARGET_SKIBOOT_XZ
-        boolean "Compress the skiboot image with XZ"
+        bool "Compress the skiboot image with XZ"
         select BR2_OPENPOWER_PNOR_XZ_ENABLED
         default y