tidy up brackets

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/library/platform_util.c b/library/platform_util.c
index 69d3d7a..2884444 100644
--- a/library/platform_util.c
+++ b/library/platform_util.c
@@ -48,7 +48,7 @@
     && !defined(__ARM_EABI__)
 #define MBEDTLS_PLATFORM_HAS_EXPLICIT_BZERO 1
 #endif
-#if defined(__FreeBSD__) && __FreeBSD_version >= 1100037
+#if defined(__FreeBSD__) && (__FreeBSD_version >= 1100037)
 #define MBEDTLS_PLATFORM_HAS_EXPLICIT_BZERO 1
 #endif
 #if defined(__NEWLIB__)