rk 屏参计算

例子如下：

  1 VOP [ff930000.vop]: DISABLED
  2 VOP [ff940000.vop]: ACTIVE
  3     Connector: LVDS
  4     overlay_mode[0] bus_format[100a] output_mode[0] color_space[0]
  5     Display mode: 1920x1080p61
  6     clk[148500] real_clk[148500] type[8] flag[a]
  7     H: 1920 1968 2000 2180
  8     V: 1080 1083 1088 1111

H: 1920 + hfront-porch = 1968， hfront-porch = 48；

    1968 + hsync-len = 2000， hsync-len = 32；

    2000 + hback-porch = 2180，hback-porch = 180；

V: 1080 + vfront-porch = 1083， vfront-porch = 3；

    1083 + vsync-len = 1088， vsync-len = 5；

    1088 + vback-porch = 1111，vback-porch = 23；