hwc: Add support for YCrCb_420_SP_VENUS(NV21_VENUS)

* Earlier, camera preview buffers were of NV21(YCrCb_420_SP)
  and the video buffers were of NV12_VENUS(YCbCr_420_SP_VENUS)
  format. Now that the video encoder has support for NV21,
  both the camera and video buffers can be of
  NV21_VENUS(YCrCb_420_SP_VENUS) format.

* If the preview and video buffer sizes are the same,
  CPP double pass to generate video and preview buffers can be
  avoided and the buffers can now be generated within a single pass
  with CPP duplication thereby saving power.

* Add support in gralloc for NV12_VENUS format to achieve
  the same.

Change-Id: I7001f975f2cafa21c893e7384ddbddd5f2788b1d
diff --git a/libgralloc/gralloc_priv.h b/libgralloc/gralloc_priv.h
index 676c3bc..a38c36c 100755
--- a/libgralloc/gralloc_priv.h
+++ b/libgralloc/gralloc_priv.h
@@ -103,6 +103,7 @@
 #define HAL_PIXEL_FORMAT_YCrCb_422_I             0x111
 #define HAL_PIXEL_FORMAT_BGRX_8888               0x112
 #define HAL_PIXEL_FORMAT_NV21_ZSL                0x113
+#define HAL_PIXEL_FORMAT_YCrCb_420_SP_VENUS      0x114
 #define HAL_PIXEL_FORMAT_INTERLACE               0x180
 
 //v4l2_fourcc('Y', 'U', 'Y', 'L'). 24 bpp YUYV 4:2:2 10 bit per component