nvdimm: fix header pointer in nvdimm_build_nfit()

In the current nvdimm_build_nfit(), the pointer 'header' initially equals
to table_data->data + table_data->len. However, the following
g_array_append_vals(table_data, structures->data, structures->len)
may resize and relocate table_data->data[]. Therefore, the usage of 'header'
afterwards may be illegal.

This patch fixes this issue by storing an offset within table_data->data[]
(rather than an address) in 'header'.

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Reviewed-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>




