Rockchip: Fix frame crop offset in H264 encoder.

According to H.264 spec, when frame_mbs_only_flag is set to 1,
frame_crop_bottom_offset should be
(pic_height_in_map_units * 16 - height) / 2.

Take 1920x1080 video for example, the value is:
- height = 1080
- pic_height_in_map_units = ((1080 + 15) >> 4) = 68
- frame_crop_bottom_offset = (68 * 16 - 1080) / 2 = 4

This CL fixed the value by adding the missing "divided by 2".

BUG=b:74214155
TEST=Run VideoEncoderDecoderTest#testAvcOther0Qual1920x1080 at device

Change-Id: I7c70564553c9e9d62b11100e214a02bba7cbb740
Reviewed-on: https://chromium-review.googlesource.com/952584


Commit-Ready: Chih-Yu Huang <akahuang@chromium.org>
Tested-by: Chih-Yu Huang <akahuang@chromium.org>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>

libv4l-rockchip_v2/libvepu/h264e/h264e.c

@@ -412,11 +412,14 @@ static int h264e_init(struct rk_venc *ictx,
 
 	if (ctx->width != ctx->sps.pic_width_in_mbs * 16 ||
 	    ctx->height != ctx->sps.pic_height_in_map_units * 16) {
+		assert(ctx->sps.frame_mbs_only_flag == 1);
+		assert(ctx->width % 2 == 0 && ctx->height % 2 == 0);
 		ctx->sps.frame_cropping_flag = 1;
 		ctx->sps.frame_crop_right_offset =
-			ctx->sps.pic_width_in_mbs * 16 - ctx->width;
+			(ctx->sps.pic_width_in_mbs * 16 - ctx->width) >> 1;
 		ctx->sps.frame_crop_bottom_offset =
-			ctx->sps.pic_height_in_map_units * 16 - ctx->height;
+			(ctx->sps.pic_height_in_map_units * 16 - ctx->height)
+			>> 1;
 	}
 
 	h264e_init_rc(ictx);