Fix parantheses on return and sizeof statements.

Used script:
```
import re
import sys

for arg in sys.argv[1:]:
    print(arg)
    with open(arg, 'r') as file:
        content = file.read()
        content = re.sub(r"return\s?\((?!.*\).*\()\s*\n?(.*)\n?\);", r"return \1;", \
            content, flags = re.M)
        content = re.sub(r"sizeof ([^\(][a-zA-Z0-9_\[\]]*)", r"sizeof(\1)",\
            content, flags = re.M)
    with open(arg, 'w') as file:
        file.write(content)

```
Executed with:
` find . -regextype posix-egrep -regex ".*\.([hc]|fmt|function)" | xargs -L1 python script.py`

Signed-off-by: Mateusz Starzyk <mateusz.starzyk@mobica.com>
diff --git a/tests/src/threading_helpers.c b/tests/src/threading_helpers.c
index ca91b79..f5a9564 100644
--- a/tests/src/threading_helpers.c
+++ b/tests/src/threading_helpers.c
@@ -160,7 +160,7 @@
             mbedtls_test_mutex_usage_error( mutex, "corrupted state" );
             break;
     }
-    return( ret );
+    return ret ;
 }
 
 static int mbedtls_test_wrap_mutex_unlock( mbedtls_threading_mutex_t *mutex )
@@ -182,7 +182,7 @@
             mbedtls_test_mutex_usage_error( mutex, "corrupted state" );
             break;
     }
-    return( ret );
+    return ret ;
 }
 
 void mbedtls_test_mutex_usage_init( void )