moveconfig: Correct list-comprehension warnings

Correct some pylint warnings about needing to use list comprehension.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/moveconfig.py b/tools/moveconfig.py
index 1dff891..d46433c 100755
--- a/tools/moveconfig.py
+++ b/tools/moveconfig.py
@@ -1422,12 +1422,12 @@
     print('\nCONFIG options present in Makefiles but not Kconfig (SPL):')
     not_found = check_not_found(all_uses, MODE_SPL)
     show_uses(not_found)
-    spl_not_found |= set([is_not_proper(key) or key for key in not_found.keys()])
+    spl_not_found |= {is_not_proper(key) or key for key in not_found.keys()}
 
     print('\nCONFIG options used as Proper in Makefiles but without a non-SPL_ variant:')
     not_found = check_not_found(all_uses, MODE_PROPER)
     show_uses(not_found)
-    proper_not_found |= set([key for key in not_found.keys()])
+    proper_not_found |= {not_found.keys()}
 
     # Scan the source code
     all_uses, _ = scan_src_files(src_list)
@@ -1440,12 +1440,12 @@
     print('\nCONFIG options present in source but not Kconfig (SPL):')
     not_found = check_not_found(all_uses, MODE_SPL)
     show_uses(not_found)
-    spl_not_found |= set([is_not_proper(key) or key for key in not_found.keys()])
+    spl_not_found |= {is_not_proper(key) or key for key in not_found.keys()}
 
     print('\nCONFIG options used as Proper in source but without a non-SPL_ variant:')
     not_found = check_not_found(all_uses, MODE_PROPER)
     show_uses(not_found)
-    proper_not_found |= set([key for key in not_found.keys()])
+    proper_not_found |= {not_found.keys()}
 
     print('\nCONFIG options used as SPL but without an SPL_ variant:')
     for item in sorted(spl_not_found):