net: pkt: Remove unnecessary error print in adjust_offset

The commit 971da9d0 ("net: pkt: adjust_offset: Simplify and optimize
code") changed the adjust_offset() function but left the error print
intact. This print is now invoked even if there is no error which
looks bad in debug prints.

Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>