Rename formats-util.h to format-util.h

We don't have plural in the name of any other -util files and this
inconsistency trips me up every time I try to type this file name
from memory. "formats-util" is even hard to pronounce.

src/udev/udev-ctrl.c

@@ -20,7 +20,7 @@
 
 #include "alloc-util.h"
 #include "fd-util.h"
-#include "formats-util.h"
+#include "format-util.h"
 #include "socket-util.h"
 #include "udev.h"
 

src/udev/udev-event.c

@@ -32,7 +32,7 @@
 
 #include "alloc-util.h"
 #include "fd-util.h"
-#include "formats-util.h"
+#include "format-util.h"
 #include "netlink-util.h"
 #include "process-util.h"
 #include "signal-util.h"

src/udev/udev-node.c

@@ -25,7 +25,7 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
-#include "formats-util.h"
+#include "format-util.h"
 #include "fs-util.h"
 #include "selinux-util.h"
 #include "smack-util.h"

src/udev/udevadm-monitor.c

@@ -26,7 +26,7 @@
 #include <time.h>
 
 #include "fd-util.h"
-#include "formats-util.h"
+#include "format-util.h"
 #include "udev-util.h"
 #include "udev.h"
 

src/udev/udevd.c

@@ -49,7 +49,7 @@
 #include "dev-setup.h"
 #include "fd-util.h"
 #include "fileio.h"
-#include "formats-util.h"
+#include "format-util.h"
 #include "fs-util.h"
 #include "hashmap.h"
 #include "io-util.h"