um: harddog: fix modular build

Since we no longer (want to) export any libc symbols the
_user portions of any drivers need to be built into image
rather than the module. I missed this for the watchdog.
Fix the watchdog accordingly.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/drivers/Makefile

@@ -16,7 +16,8 @@ mconsole-objs := mconsole_kern.o mconsole_user.o
 hostaudio-objs := hostaudio_kern.o
 ubd-objs := ubd_kern.o ubd_user.o
 port-objs := port_kern.o port_user.o
-harddog-objs := harddog_kern.o harddog_user.o
+harddog-objs := harddog_kern.o
+harddog-builtin-$(CONFIG_UML_WATCHDOG) := harddog_user.o harddog_user_exp.o
 rtc-objs := rtc_kern.o rtc_user.o
 
 LDFLAGS_pcap.o = $(shell $(CC) $(KBUILD_CFLAGS) -print-file-name=libpcap.a)
@@ -60,6 +61,7 @@ obj-$(CONFIG_PTY_CHAN) += pty.o
 obj-$(CONFIG_TTY_CHAN) += tty.o 
 obj-$(CONFIG_XTERM_CHAN) += xterm.o xterm_kern.o
 obj-$(CONFIG_UML_WATCHDOG) += harddog.o
+obj-y += $(harddog-builtin-y) $(harddog-builtin-m)
 obj-$(CONFIG_BLK_DEV_COW_COMMON) += cow_user.o
 obj-$(CONFIG_UML_RANDOM) += random.o
 obj-$(CONFIG_VIRTIO_UML) += virtio_uml.o