drm/vmwgfx: Initialize drm_mode_fb_cmd2

Transition to drm_mode_fb_cmd2 from drm_mode_fb_cmd left the structure
unitialized. drm_mode_fb_cmd2 adds a few additional members, e.g. flags
and modifiers which were never initialized. Garbage in those members
can cause random failures during the bringup of the fbcon.

Initializing the structure fixes random blank screens after bootup due
to flags/modifiers mismatches during the fbcon bring up.

Fixes: dabdcdc9 ("drm/vmwgfx: Switch to mode_cmd2")
Signed-off-by: Zack Rusin <zackr@vmware.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: <stable@vger.kernel.org> # v4.10+
Reviewed-by: Martin Krastev <krastevm@vmware.com>
Reviewed-by: Maaz Mombasawala <mombasawalam@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220302152426.885214-7-zack@kde.org

drivers/gpu/drm/vmwgfx/vmwgfx_fb.c

@@ -483,7 +483,7 @@ static int vmw_fb_kms_detach(struct vmw_fb_par *par,
 
 static int vmw_fb_kms_framebuffer(struct fb_info *info)
 {
-	struct drm_mode_fb_cmd2 mode_cmd;
+	struct drm_mode_fb_cmd2 mode_cmd = {0};
 	struct vmw_fb_par *par = info->par;
 	struct fb_var_screeninfo *var = &info->var;
 	struct drm_framebuffer *cur_fb;