hwc/copybit: Handle "R/B swap" for RGBA and RGBX color formats.

1.Framework notifies HAL with "HWC_FORMAT_RB_SWAP" layer flag to handle
a limitation where R and B components were swapped in Rendering phase.
2.Add "R/B swap" in hwc query to enable framework to query for support
in display HAL, at run-time.

Change-Id: I3b44d15b51b4f24939048fee9d1bac2b9009c97c
diff --git a/libhwcomposer/hwc.cpp b/libhwcomposer/hwc.cpp
index ec9abfb..5038025 100644
--- a/libhwcomposer/hwc.cpp
+++ b/libhwcomposer/hwc.cpp
@@ -446,6 +446,9 @@
             supported |= HWC_DISPLAY_EXTERNAL_BIT;
         value[0] = supported;
         break;
+    case HWC_FORMAT_RB_SWAP:
+        value[0] = 1;
+        break;
     default:
         return -EINVAL;
     }