ESYS: Correct default tcti handling

Pass the default tcti module and config as
strings into C.

Signed-off-by: Andreas Fuchs <andreas.fuchs@sit.fraunhofer.de>
diff --git a/configure.ac b/configure.ac
index dc33d0e..6fade53 100644
--- a/configure.ac
+++ b/configure.ac
@@ -118,7 +118,7 @@
             [AS_HELP_STRING([--with-tctidefaultmodule],
 [The default TCTI module for ESAPI. (Default: libtss2-tcti-default.so])],
             [AC_DEFINE_UNQUOTED([ESYS_TCTI_DEFAULT_MODULE],
-                                [$with_tctidefaultmodule],
+                                ["$with_tctidefaultmodule"],
                                 ["The default TCTI library file"])],
             [])
 
@@ -126,7 +126,7 @@
             [AS_HELP_STRING([--with-tctidefaultconfig],
                             [The default tcti module's configuration.])],
             [AC_DEFINE_UNQUOTED([ESYS_TCTI_DEFAULT_CONFIG],
-                                [$with_tctidefaultconfig],
+                                ["$with_tctidefaultconfig"],
                                 ["The default TCTIs configuration string"])],
             [])