net: wwan: iosm: fix lkp buildbot warning

Correct td buffer type casting & format specifier to fix lkp buildbot
warning.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: M Chetan Kumar <m.chetan.kumar@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>