tps6598x: fix val warning

Signed-off-by: Angus Ainslie <angus@akkea.ca>
2 jobs for librem5-extcon-5.7 in 50 minutes and 32 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #270146
librem5
build:aarch64

00:18:51

passed #270147
librem5:arm64
build:deb

00:50:31