bnxt_en: Rename some macros for the P5 chips

In preparation to support a new P7 chip which has a lot of similarities
with the P5 chip, rename the BNXT_FLAG_CHIP_P5 flag to
BNXT_FLAG_CHIP_P5_PLUS.  This will make it clear that the flag is for
P5 and newer chips.

Also, since there are no additional P5 variants in production, rename
BNXT_FLAG_CHIP_P5_THOR() to BNXT_FLAG_CHIP_P5() to keep the naming
more simple.

Reviewed-by: Andy Gospodarek <andrew.gospodarek@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Signed-off-by: Randy Schacher <stuart.schacher@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Link: https://lore.kernel.org/r/20231120234405.194542-14-michael.chan@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>