net: phy: mediatek: add driver for built-in 2.5G ethernet PHY on MT7988

net: phy: mediatek: add driver for built-in 2.5G ethernet PHY on MT7988

Add support for internal 2.5Gphy on MT7988. This driver will load
necessary firmware and add appropriate time delay to make sure
that firmware works stably. The firmware loading procedure takes
about 11ms in this driver.

Signed-off-by: Sky Huang <skylake.huang@mediatek.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20250516102327.2014531-3-SkyLake.Huang@mediatek.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>