ice: Clean up register file

This patch cleans up the existing register definitions.

1) Several instances of long defines names used in the BIT() macro
   were replaced to use the actual values they represent. As a
   result some defines for shifts (ending with _S) that were used
   only to create bitmasks were removed completely.

2) Apply more consistent tab spacing.

Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Tested-by: Tony Brelinski <tonyx.brelinski@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>