phosphor-led-sysfs: use c++17

Update configure.ac to choose the c++17 standard

Change-Id: I4dac04257a7b6758d28c8639d1ced9651cfaca90
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
diff --git a/configure.ac b/configure.ac
index 6a08be3..58e557a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -15,7 +15,7 @@
 PKG_CHECK_MODULES([SYSTEMD], [libsystemd >= 221])
 
 # Checks for typedefs, structures, and compiler characteristics.
-AX_CXX_COMPILE_STDCXX_14([noext])
+AX_CXX_COMPILE_STDCXX_17([noext])
 AX_APPEND_COMPILE_FLAGS([-Wall -Werror], [CXXFLAGS])
 
 # For libtools