android: Fix goldfish_fb virtual device.

A small bug prevented the emulated framebuffer device to send
pixels to the video output. This patch fixes this, which makes
'-gpu off' and '-gpu guest' work again.

BUG=33180552

Change-Id: If31be2e77210259de483fde176d50c37bda77402

hw/display/goldfish_fb.c

diff --git a/hw/display/goldfish_fb.c b/hw/display/goldfish_fb.c
index 3c0820a..e4ac3de 100644
--- a/hw/display/goldfish_fb.c
+++ b/hw/display/goldfish_fb.c
@@ -349,7 +349,7 @@
         // CPU time on OSX; saving on other platforms may differ.
         if (s_use_host_gpu) return;
 
-        if (s->need_update) {
+        if (full_update) {
             framebuffer_update_memory_section(
                     &s->fbsection, get_system_memory(), s->fb_base,
                     src_height, src_width * source_bytes_per_pixel);