net:hns: annotate IO address space properly

Mark address pointer with __iomem in the IO accessors.

Otherwise we will get a sparse complain like following

.../hns/hns_dsaf_reg.h:991:36: warning: incorrect type in argument 1 (different address spaces)
.../hns/hns_dsaf_reg.h:991:36:    expected unsigned char [noderef] [usertype] <asn:2>*base
.../hns/hns_dsaf_reg.h:991:36:    got void *base

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>