Allow RGBX8888 in soft video encoder

BUG=27844478,28550227
TEST=android.hardware.camera2.cts.RecordingTest will pass
Change-Id: Ib669d4a2447bb5d76b9d0cdc34469cad77a98ee2
diff --git a/media/libstagefright/omx/SoftVideoEncoderOMXComponent.cpp b/media/libstagefright/omx/SoftVideoEncoderOMXComponent.cpp
index c3a481a..0f9c118 100644
--- a/media/libstagefright/omx/SoftVideoEncoderOMXComponent.cpp
+++ b/media/libstagefright/omx/SoftVideoEncoderOMXComponent.cpp
@@ -625,6 +625,7 @@
         case HAL_PIXEL_FORMAT_YCbCr_420_888:
             ConvertFlexYUVToPlanar(dst, dstStride, dstVStride, &ycbcr, width, height);
             break;
+        case HAL_PIXEL_FORMAT_RGBX_8888:
         case HAL_PIXEL_FORMAT_RGBA_8888:
         case HAL_PIXEL_FORMAT_BGRA_8888:
             ConvertRGB32ToPlanar(