net: macb: Add 64 bit addressing support for GEM

net: macb: Add 64 bit addressing support for GEM

This patch adds support for 64 bit addressing and BDs.
-> Enable 64 bit addressing in DMACFG register.
-> Set DMA mask when design config register shows support for 64 bit addr.
-> Add new BD words for higher address when 64 bit DMA support is present.
-> Add and update TBQPH and RBQPH for MSB of BD pointers.
-> Change extraction and updation of buffer addresses to use
64 bit address.
-> In gem_rx extract address in one place insted of two and use a
separate flag for RXUSED.

Signed-off-by: Harini Katakam <harinik@xilinx.com>
Signed-off-by: David S. Miller <davem@davemloft.net>