Cleanup: Use filesystem instead of experimental

The GCC version bump in Yocto 2.6 allows for use of std::filesystem
instead of std::experimental::filesystem.

Change-Id: Ibfd6c285bcbd6695e5cd4e3090ffa214fc861499
Signed-off-by: Brandon Wyman <bjwyman@gmail.com>
diff --git a/power-sequencer/ucd90160.cpp b/power-sequencer/ucd90160.cpp
index 08b8a7d..203004d 100644
--- a/power-sequencer/ucd90160.cpp
+++ b/power-sequencer/ucd90160.cpp
@@ -41,7 +41,7 @@
 
 constexpr auto INVENTORY_OBJ_PATH = "/xyz/openbmc_project/inventory";
 
-namespace fs = std::experimental::filesystem;
+namespace fs = std::filesystem;
 using namespace gpio;
 using namespace pmbus;
 using namespace phosphor::logging;