Check if the last word is 'MASK', not if it ends with 'MASK'

At the moment it makes no difference, but it could if e.g. a new
algorithm was called 'foomask'.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

scripts/mbedtls_dev/macro_collector.py

@@ -50,7 +50,7 @@ class PSAMacroCollector:
                 return True
             if '_CATEGORY_' in name:
                 return True
-        return name.endswith('_FLAG') or name.endswith('MASK')
+        return name.endswith('_FLAG') or name.endswith('_MASK')
 
     # "#define" followed by a macro name with either no parameters
     # or a single parameter and a non-empty expansion.