nwl: Don't turn off clocks and phy on screen blank

This makes the display turn on again on unblank like

    echo 1 > /sys/class/graphics/fb0/blank ; sleep 1; echo 0 > /sys/class/graphics/fb0/blank

Closes: #32

Signed-off-by: Guido Günther <guido.gunther@puri.sm>
2 jobs for imx8-4.18-devkit-dsi-no_clk_reset
in 48 minutes and 35 seconds, using 0.0 compute credits, and was queued for 3 seconds