ia64: remove unused num_dma_physpages member from 'struct early_node_data'

Since commit 05e0caad

 ("[PATCH] Have ia64 use add_active_range() and
free_area_init_nodes") the num_dma_physpages member of 'struct
early_node_data' is calculated but never used. Remove it.

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>