Force the fb into 16 bpp mode in case the hw has some other default.

Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>

minui/graphics.c

@@ -115,6 +115,7 @@ static void set_active_framebuffer(unsigned n)
     if (n > 1) return;
     vi.yres_virtual = vi.yres * 2;
     vi.yoffset = n * vi.yres;
+    vi.bits_per_pixel = 16;
     if (ioctl(gr_fb_fd, FBIOPUT_VSCREENINFO, &vi) < 0) {
         perror("active fb swap failed");
     }