sdbus++: handle 'DHCP{4,6}' better

The enum identifier 'DHCP4' was becoming 'dhcP4'.  Revise the
`lower_camel_case` function to better handle this so it becomes
'dhcp4'.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Id999c4873e7c4c914dd03acd46144365aec066db
diff --git a/tools/sdbusplus/namedelement.py b/tools/sdbusplus/namedelement.py
index c7985cf..c41d451 100644
--- a/tools/sdbusplus/namedelement.py
+++ b/tools/sdbusplus/namedelement.py
@@ -151,7 +151,7 @@
         upper_name = inflection.camelize(name)
 
         # If it is all upper case, return as all lower.  ex. "MAC"
-        if re.match(r"^[A-Z]*$", upper_name):
+        if re.match(r"^[A-Z0-9]*$", upper_name):
             return upper_name.lower()
 
         # If it doesn't start with 2 upper case, it isn't an acronym.