Fix an incorrect regex in check_names.py

Allow check_names.py to detect declarations of the form:

enum some_enum_name {

This pattern has only just appeared due to code style correction, which
explains why the issue was not previously noticed.

Signed-off-by: David Horstmann <david.horstmann@arm.com>
diff --git a/tests/scripts/check_names.py b/tests/scripts/check_names.py
index 13b6c2d..7398f3c 100755
--- a/tests/scripts/check_names.py
+++ b/tests/scripts/check_names.py
@@ -444,8 +444,11 @@
                     # Match typedefs and brackets only when they are at the
                     # beginning of the line -- if they are indented, they might
                     # be sub-structures within structs, etc.
+                    optional_c_identifier = r"([_a-zA-Z][_a-zA-Z0-9]*)?"
                     if (state == states.OUTSIDE_KEYWORD and
-                            re.search(r"^(typedef +)?enum +{", line)):
+                            re.search(r"^(typedef +)?enum " + \
+                                    optional_c_identifier + \
+                                    r" *{", line)):
                         state = states.IN_BRACES
                     elif (state == states.OUTSIDE_KEYWORD and
                           re.search(r"^(typedef +)?enum", line)):