Compile device-hotplug on all targets

All guest targets could potentially implement hotplugging. With the next
patches in this set I will also reflect this in the monitor interface.

So let's always compile it in. It shouldn't hurt.
Signed-off-by: NAlexander Graf <agraf@suse.de>

Makefile.target

@@ -220,12 +220,15 @@ ifeq ($(CONFIG_KVM), y)
 endif
 obj-$(CONFIG_IVSHMEM) += ivshmem.o
 
+# Generic hotplugging
+obj-y += device-hotplug.o
+
 # Hardware support
 obj-i386-y += vga.o
 obj-i386-y += mc146818rtc.o pc.o
 obj-i386-y += cirrus_vga.o sga.o apic.o ioapic.o piix_pci.o
 obj-i386-y += vmport.o
-obj-i386-y += device-hotplug.o pci-hotplug.o smbios.o wdt_ib700.o
+obj-i386-y += pci-hotplug.o smbios.o wdt_ib700.o
 obj-i386-y += debugcon.o multiboot.o
 obj-i386-y += pc_piix.o
 obj-i386-$(CONFIG_KVM) += kvmclock.o