btrfs-progs: move cmds-send.c to cmds/

Signed-off-by: David Sterba <dsterba@suse.com>

Makefile

@@ -136,7 +136,7 @@ objects = ctree.o disk-io.o kernel-lib/radix-tree.o extent-tree.o print-tree.o \
 	  fsfeatures.o kernel-lib/tables.o kernel-lib/raid56.o transaction.o \
 	  delayed-ref.o
 cmds_objects = cmds/subvolume.o cmds/filesystem.o cmds/device.o cmds/scrub.o \
-	       cmds/inspect.o cmds/balance.o cmds-send.o cmds/receive.o \
+	       cmds/inspect.o cmds/balance.o cmds/send.o cmds/receive.o \
 	       cmds/quota.o cmds/qgroup.o cmds/replace.o check/main.o \
 	       cmds/restore.o cmds/rescue.o cmds/rescue-chunk-recover.o \
 	       cmds/rescue-super-recover.o \