platform/mellanox: mlxbf-pmc: Fix reading of unprogrammed events

This fix involves 2 changes:
 - All event regs have a reset value of 0, which is not a valid
   event_number as per the event_list for most blocks and hence seen
   as an error. Add a "disable" event with event_number 0 for all blocks.

 - The enable bit for each counter need not be checked before
   reading the event info, and hence removed.

Fixes: 1a218d31 ("platform/mellanox: mlxbf-pmc: Add Mellanox BlueField PMC driver")
Signed-off-by: Shravan Kumar Ramani <shravankr@nvidia.com>
Reviewed-by: Vadim Pasternak <vadimp@nvidia.com>
Reviewed-by: David Thompson <davthompson@nvidia.com>
Link: https://lore.kernel.org/r/04d0213932d32681de1c716b54320ed894e52425.1693917738.git.shravankr@nvidia.com


Signed-off-by: Hans de Goede <hdegoede@redhat.com>