clk: rockchip: rk3399: keep the pclk_vio is CLK_IGNORE_UNUSED and critical

clk: rockchip: rk3399: keep the pclk_vio is CLK_IGNORE_UNUSED and critical

When we use the MIPI screen, the driver will unprepare and disable
the phy_cfg, it will diable its parent pclk_vio:
dw_mipi_dsi_phy_init
  --> clk_disable_unprepare
    --> clk_disable
      --> clk_core_disable(core->parent)

The pclk_vio supply power for pclk_vio_grf, hence, disable pclk_vio_grf will
cause other drivers failed to operate GRF.

Change-Id: I6d5bd27b9478da09209130f1fd5a62c0d4bb1785
Reported-by: Yakir Yang <ykk@rock-chips.com>
Signed-off-by: Xing Zheng <zhengxing@rock-chips.com>