fm10k: reduce duplicate fm10k_stat macro code

Share some of the code for setting up fm10k_stat macros by implementing
an FM10K_STAT_FIELDS macro which we can use when setting up the type
specific macros.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Krishneil Singh <krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>