net/bnxt: refactor and rename some fields and enums

net/bnxt: refactor and rename some fields and enums

- rename regfile_wr_idx to regfile_idx
  The regfile index shall be used for both write and read operations.
  Hence the field is renamed.
- remove the unused enum BNXT_ULP_REGFILE_INDEX_CACHE_ENTRY_PTR
- rename the enums in the bnxt_ulp_resource_sub_type
  The enums in the bnxt_ulp_resource_sub_type are renamed to reflect
  the table types explicitly.
- rename an enum in the regfile index
  The BNXT_ULP_REGFILE_INDEX_ACTION_PTR_MAIN is renamed to
  BNXT_ULP_REGFILE_INDEX_MAIN_ACTION_PTR since it is the main
  action pointer.
- remove cache_tbl_id enums
  The bnxt_ulp_cache_tbl_id enums are not required any longer
  since the index is now calculated using resource sub type
  and direction.

Signed-off-by: Kishore Padmanabha <kishore.padmanabha@broadcom.com>
Reviewed-by: Venkat Duvvuru <venkatkumar.duvvuru@broadcom.com>
Reviewed-by: Mike Baucom <michael.baucom@broadcom.com>
Signed-off-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>