net_tstamp: Add TIMESTAMPING SOFTWARE and HARDWARE mask

Timestamping software or hardware flags are often used as a group,
therefore adding these masks will ease future use.

I did not use SOF_TIMESTAMPING_SYS_HARDWARE flag as it is deprecated and
not used at all.

Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Link: https://patch.msgid.link/20240709-feature_ptp_netnext-v17-1-b5317f50df2a@bootlin.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>