ixgbe: add array of MAC type dependent values

Some of the register addresses and format where unfortunately changed
between MAC types. To get around this we add a const u32 *mvals pointer
to the ixgbe_hw struct to point to an array of mac-type-dependent
values.  These can include register offsets, masks, whatever can be in
a u32. When the ixgbe_hw struct is initialized, a pointer to the
appropriate array must be set.

Signed-off-by: Don Skidmore <donald.c.skidmore@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>