dm dust: remove h from printk format specifier

See Documentation/core-api/printk-formats.rst.

commit cbacb5ab ("docs: printk-formats: Stop encouraging use of unnecessary %h[xudi] and %hh[xudi]")

Standard integer promotion is already done and %hx and %hhx is useless
so do not encourage the use of %hh[xudi] or %h[xudi].

Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>