Merge branch 'riscv-sophgo-add-ethernet-support-for-sg2042'

Inochi Amaoto says:

====================
riscv: sophgo: Add ethernet support for SG2042

The ethernet controller of SG2042 is Synopsys DesignWare IP with
tx clock. Add device id for it.

This patch can only be tested on a SG2042 evb board, as pioneer
does not expose this device.

The user dts patch link:
https://lore.kernel.org/linux-riscv/cover.1751700954.git.rabenda.cn@gmail.com
====================

Link: https://patch.msgid.link/20250708064052.507094-1-inochiama@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>