Fix docs for mbedtls_padlock_has_support

Fix a slight inaccuracy in the docs for the return value of
mbedtls_padlock_has_support.

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/padlock.h b/library/padlock.h
index 78dbeb6..4f4e400 100644
--- a/library/padlock.h
+++ b/library/padlock.h
@@ -71,7 +71,7 @@
  *
  * \param feature  The feature to detect
  *
- * \return         1 if CPU has support for the feature, 0 otherwise
+ * \return         non-zero if CPU has support for the feature, 0 otherwise
  */
 int mbedtls_padlock_has_support( int feature );