net: stmmac: socfpga: Add hardware supported cross-timestamp

net: stmmac: socfpga: Add hardware supported cross-timestamp

Cross timestamping is supported on Agilex5 platform with Synchronized
Multidrop Timestamp Gathering(SMTG) IP. The hardware cross-timestamp
result is made available the applications through the ioctl call
PTP_SYS_OFFSET_PRECISE, which inturn calls stmmac_getcrosststamp().

Device time is stored in the MAC Auxiliary register. The 64-bit System
time (ARM_ARCH_COUNTER) is stored in SMTG IP. SMTG IP is an MDIO device
with 0xC - 0xF MDIO register space holds 64-bit system time.

This commit is similar to following commit for Intel platforms:
Commit 341f67e424e5 ("net: stmmac: Add hardware supported cross-timestamp")

Signed-off-by: Rohan G Thomas <rohan.g.thomas@altera.com>
Link: https://patch.msgid.link/20251101-agilex5_ext-v2-4-a6b51b4dca4d@altera.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>