drm/vmwgfx: fix typo of sizeof argument

Since size of 'header' pointer and '*header' structure is equal on 64-bit
machines issue probably didn't cause any wrong behavior. But anyway,
fixing typo is required.

Fixes: 7a73ba74 ("drm/vmwgfx: Use TTM handles instead of SIDs as user-space surface handles.")
Co-developed-by: Ivanov Mikhail <ivanov.mikhail1@huawei-partners.com>
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@huawei.com>
Reviewed-by: Zack Rusin <zackr@vmware.com>
Signed-off-by: Zack Rusin <zackr@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230905100203.1716731-1-konstantin.meskhidze@huawei.com

drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c

@@ -1619,7 +1619,7 @@ static int vmw_cmd_tex_state(struct vmw_private *dev_priv,
 {
 	VMW_DECLARE_CMD_VAR(*cmd, SVGA3dCmdSetTextureState);
 	SVGA3dTextureState *last_state = (SVGA3dTextureState *)
-	  ((unsigned long) header + header->size + sizeof(header));
+	  ((unsigned long) header + header->size + sizeof(*header));
 	SVGA3dTextureState *cur_state = (SVGA3dTextureState *)
 		((unsigned long) header + sizeof(*cmd));
 	struct vmw_resource *ctx;