set installer image size to 3GB on ppc64le

fixes https://pagure.io/releng/issue/8059 and https://bugzilla.redhat.com/show_bug.cgi?id=1666298

Signed-off-by: Dan Horák <dan@danny.cz>

fedora.conf

@@ -101,12 +101,16 @@ buildinstall_skip = [
 ]
 
 # Enables macboot on x86_64 for all variants and disables upgrade image building
-# # everywhere.
+# everywhere.
+# Use 3GB image size for ppc64le.
 lorax_options = [
   ('^.*$', {
      'x86_64': {
          'nomacboot': False
      },
+     'ppc64le': {
+         'rootfs_size': 3
+     },
      '*': {
          'noupgrade': True
      }