ptp_pch: eliminate a number of sparse warnings

This fixes a number of sparse warnings like:
  warning: incorrect type in argument 2 (different address spaces)
    expected void volatile [noderef] <asn:2>*addr
    got unsigned int *<noident>

  warning: Using plain integer as NULL pointer

Additionally this fixes a warning from checkpatch.pl like:
  WARNING: sizeof pch_param.station should be sizeof(pch_param.station)

Signed-off-by: Sahara <keun-o.park@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>