[rhine] Rewrite VIA Rhine driver

Replace the old via-rhine driver with a new version using the iPXE
API.

Includes fixes by Thomas Miletich for:

  - MMIO access
  - Link detection
  - RX completion in RX overflow case
  - Reset and EEPROM reloading
  - CRC stripping
  - Missing cpu_to_le32() calls
  - Missing memory barriers

Signed-off-by: Adrian Jamróz <adrian.jamroz@gmail.com>
Modified-by: Thomas Miletich <thomas.miletich@gmail.com>
Tested-by: Thomas Miletich <thomas.miletich@gmail.com>
Tested-by: Robin Smidsrød <robin@smidsrod.no>
Modified-by: Michael Brown <mcb30@ipxe.org>
Tested-by: Michael Brown <mcb30@ipxe.org>
Signed-off-by: Michael Brown <mcb30@ipxe.org>