unicore32-softmmu: Add puv3 gpio support

This patch adds puv3 gpio (General Purpose Input/Output) support,
include gpio device simulation and its interrupt support.

v1->v2: Add initialization to ret in puv3_gpio_read.

Signed-off-by: Guan Xuetao <gxt@mprc.pku.edu.cn>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/hw/Makefile.objs b/hw/Makefile.objs
index 583dd6d..0e6ad8c 100644
--- a/hw/Makefile.objs
+++ b/hw/Makefile.objs
@@ -69,6 +69,7 @@
 # PKUnity SoC devices
 hw-obj-$(CONFIG_PUV3) += puv3_intc.o
 hw-obj-$(CONFIG_PUV3) += puv3_ost.o
+hw-obj-$(CONFIG_PUV3) += puv3_gpio.o
 
 # PCI watchdog devices
 hw-obj-$(CONFIG_PCI) += wdt_i6300esb.o