un-export mount.FMountat

It's only used internally, so we can un-export this utility until
it is needed elsewhere.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

mount/fmountat_linux.go

@@ -26,8 +26,8 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-// FMountat performs mount from the provided directory.
-func FMountat(dirfd uintptr, source, target, fstype string, flags uintptr, data string) error {
+// fMountat performs mount from the provided directory.
+func fMountat(dirfd uintptr, source, target, fstype string, flags uintptr, data string) error {
 	var (
 		sourceP, targetP, fstypeP, dataP *byte
 		pid                              uintptr