dts: Replace status = "ok" with status = "okay"

The DT spec. only has "okay" and not "ok". The Linux kernel has around
12k "okay"s and 300 "ok"s.

The scripts/dts scripts only check for "disabled", so should be safe re.
those at least.

The replacement was done with

    git ls-files | xargs sed -i 's/status\s*=\s*"ok"/status = "okay"/'

Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>