bootdevice: move bootdevice related code to new file bootdevice.c

Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
diff --git a/Makefile.target b/Makefile.target
index 1e8d7ab..e9ff1ee 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -127,7 +127,7 @@
 # System emulator target
 ifdef CONFIG_SOFTMMU
 obj-y += arch_init.o cpus.o monitor.o gdbstub.o balloon.o ioport.o numa.o
-obj-y += qtest.o
+obj-y += qtest.o bootdevice.o
 obj-y += hw/
 obj-$(CONFIG_FDT) += device_tree.o
 obj-$(CONFIG_KVM) += kvm-all.o