clang-tidy: Enable readability-uppercase-literal-suffix check

cert-dcl16-c redirects here as an alias for this check. By default,
only the suffixes that begin with l (l, ll, lu, llu, but not u, ul,
ull) are diagnosed by that alias.

Signed-off-by: George Liu <liuxiwei@ieisystem.com>
Change-Id: I180ee3e3274899c63181f69a14f158319f178f0c
diff --git a/.clang-tidy b/.clang-tidy
index 0b9563b..2c7ef0a 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -251,7 +251,8 @@
 readability-static-accessed-through-instance,
 readability-static-definition-in-anonymous-namespace,
 readability-suspicious-call-argument,
-readability-uniqueptr-delete-release'
+readability-uniqueptr-delete-release,
+readability-uppercase-literal-suffix'
 
 WarningsAsErrors: '*'
 HeaderFilterRegex: '.*'