mm-video-vidc: change buffer index logic in EBD

with current logic video perf CTS use cases are failing,
also use proxy color format flag to get buffer index value
in EBD.

Change-Id: Iac1730230dbdedff062d2374dbbb966348765cb4
diff --git a/mm-video-v4l2/vidc/venc/src/omx_video_base.cpp b/mm-video-v4l2/vidc/venc/src/omx_video_base.cpp
index 3da4f9e..027a6dd 100644
--- a/mm-video-v4l2/vidc/venc/src/omx_video_base.cpp
+++ b/mm-video-v4l2/vidc/venc/src/omx_video_base.cpp
@@ -3962,7 +3962,7 @@
 {
     int buffer_index  = -1;
 
-    buffer_index = buffer - (mUsesColorConversion ? m_inp_mem_ptr : meta_buffer_hdr);
+    buffer_index = buffer - ((mUseProxyColorFormat && !mUsesColorConversion) ? meta_buffer_hdr : m_inp_mem_ptr);
     DEBUG_PRINT_LOW("empty_buffer_done: buffer[%p]", buffer);
     if (buffer == NULL ||
             ((buffer_index > (int)m_sInPortDef.nBufferCountActual))) {