platform/mellanox: mlxbf-tmfifo: Fix a warning message

This commit fixes the smatch static checker warning in function
mlxbf_tmfifo_rxtx_word() which complains data not initialized at
line 634 when IS_VRING_DROP() is TRUE.

Signed-off-by: Liming Sun <limings@nvidia.com>
Link: https://lore.kernel.org/r/20231012230235.219861-1-limings@nvidia.com


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