Kconfig: Fix "warning: style: quotes recommended" warnings

We have three warnings about needing to use quotes around some strings
in Kconfig files today. In two of these cases we can just add the
missing strings. In the case of INTEL_PINCTRL_PADCFG_PADTOL the symbol
is never referenced and should be dropped.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/lib/Kconfig b/lib/Kconfig
index a21b337..1795446 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -445,7 +445,9 @@
 source "lib/dhry/Kconfig"
 
 menu "Alternative crypto libraries"
-source lib/mbedtls/Kconfig
+
+source "lib/mbedtls/Kconfig"
+
 endmenu
 
 menu "Security support"