net/sfc/base: report memory BAR number

net/sfc/base: report memory BAR number

On Medford and earlier controllers the BAR layout is:
  PF BAR 0: (32bit I/O) I/O mapped registers
  PF BAR 2: (64bit Mem) Memory mapped registers (VI aperture)
  PF BAR 4: (64bit Mem) MSI-X tables

  VF BAR 0: (64bit Mem) Memory mapped registers (VI aperture)
  VF BAR 2: (64bit Mem) MSI-X tables

On Medford2, the layout is:
  PF/VF BAR 0: (64bit Mem) Memory mapped registers (VI aperture)
  PF/VF BAR 2: (64bit Mem) MSI-X tables

Make the VI aperture BAR number available for drivers that need it.
Remove EFX_MEM_BAR define as it it is not correct on all platforms.

Signed-off-by: Andy Moreton <amoreton@solarflare.com>
Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>