platform/mellanox: mlxbf-tmfifo: Remove unnecessary bool conversion

This commit fixes coccinelle warning in macro function
IS_VRING_DROP() which complains conversion to bool not needed here.

Signed-off-by: Jules Irenge <jbi.octave@gmail.com>
Link: https://lore.kernel.org/r/ZUWIIKbz4vukl8qb@octinomon
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>