ixgbe/base: rework mac-type-dependent constants

ixgbe/base: rework mac-type-dependent constants

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.

The IXGBE_I2CCTL register references are changed to use it.
Use the mvals array to hold differing values used for
IXGBE_I2C_* symbols.
Use the mvals array to hold differing values used for
IXGBE_*_GPI* symbols.
Use the mvals array to hold differing values use for CIAA and
CIAD symbols.

Signed-off-by: Wenzhuo Lu <wenzhuo.lu@intel.com>
Acked-by: Helin Zhang <helin.zhang@intel.com>