Fix comparison of boolean values in CMake build.

Follow-up of 70c4097b6f.

Signed-off-by: Timo Gurr <timo.gurr@gmail.com>

CMakeLists.txt

@@ -55,13 +55,13 @@ if (WITH_TLS)
 	find_package(OpenSSL REQUIRED)
 	add_definitions("-DWITH_TLS")
 
-	if (${WITH_TLS_PSK} STREQUAL ON)
+	if (WITH_TLS_PSK)
 		add_definitions("-DWITH_TLS_PSK")
-	endif (${WITH_TLS_PSK} STREQUAL ON)
+	endif (WITH_TLS_PSK)
 
-	if (${WITH_EC} STREQUAL ON)
+	if (WITH_EC)
 		add_definitions("-DWITH_EC")
-	endif (${WITH_EC} STREQUAL ON)
+	endif (WITH_EC)
 else (WITH_TLS)
 	set (OPENSSL_INCLUDE_DIR "")
 endif (WITH_TLS)