lib/fs: Fix format string in find_fs_mount()

A field width of 4096 allows fscanf() to store that amount of characters
into the given buffer, though that doesn't include the terminating NULL
byte. Decrease the value by one to leave space for it.

Signed-off-by: Phil Sutter <phil@nwl.cc>

lib/fs.c

@@ -45,7 +45,7 @@ static char *find_fs_mount(const char *fs_to_find)
 		return NULL;
 	}
 
-	while (fscanf(fp, "%*s %4096s %127s %*s %*d %*d\n",
+	while (fscanf(fp, "%*s %4095s %127s %*s %*d %*d\n",
 		      path, fstype) == 2) {
 		if (strcmp(fstype, fs_to_find) == 0) {
 			mnt = strdup(path);