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 37 minutes and 49 seconds (queued for 30 minutes and 34 seconds)
Status Name Job ID Coverage
  Build
passed build:aarch64:Image #17690
librem5

00:37:49

passed build:aarch64:deb #17691
librem5

00:24:22