hw/core: nmi.c can be compiled as common-obj nowadays

The target-specific code in nmi.c has been removed with this commit:

	commit f7e981f29548fe4af7812f5920304fe607e5bf0d
	nmi: remove x86 specific nmi handling

Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

hw/core/Makefile.objs

@@ -5,7 +5,7 @@ common-obj-y += fw-path-provider.o
 # irq.o needed for qdev GPIO handling:
 common-obj-y += irq.o
 common-obj-y += hotplug.o
-obj-y += nmi.o
+common-obj-y += nmi.o
 
 common-obj-$(CONFIG_EMPTY_SLOT) += empty_slot.o
 common-obj-$(CONFIG_XILINX_AXI) += stream.o