usb: typec: tps6598x: Add debugfs entries for customer use word

This allows to verify that a sane firmware is on the device.

Signed-off-by: Guido Günther <agx@sigxcpu.org>
2 jobs for usb-c-current in 74 minutes and 5 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Build
passed build:aarch64 #320417
librem5

00:41:54

passed build:deb #320418
librem5:arm64

01:14:05