x86/platform/uv: Rework NMI "action" modparam handling

Rework NMI "action" modparam handling:

 - Replace the uv_nmi_action string with an enum; and
 - Use sysfs_match_string() for string parsing in param_set_action()

No change in functionality intended.

Suggested-by: Steve Wahl <steve.wahl@hpe.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Steve Wahl <steve.wahl@hpe.com>
Reviewed-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Steve Wahl <steve.wahl@hpe.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20230916130653.243532-1-hdegoede@redhat.com