hwc: Add support for plane alpha

HWC 1.2 API passes down the plane alpha and the blending
operation to apply. Pass this information to the MDP.

Change-Id: I7fbd17345d9157aa654e4b1031ac3e26adf87f37
diff --git a/libhwcomposer/hwc.cpp b/libhwcomposer/hwc.cpp
index f90420f..4b0ff9a 100644
--- a/libhwcomposer/hwc.cpp
+++ b/libhwcomposer/hwc.cpp
@@ -751,7 +751,7 @@
 
         //Setup HWC methods
         dev->device.common.tag          = HARDWARE_DEVICE_TAG;
-        dev->device.common.version      = HWC_DEVICE_API_VERSION_1_1;
+        dev->device.common.version      = HWC_DEVICE_API_VERSION_1_2;
         dev->device.common.module       = const_cast<hw_module_t*>(module);
         dev->device.common.close        = hwc_device_close;
         dev->device.prepare             = hwc_prepare;