net: stmmac: Enable timestamping interrupt on dwmac1000

net: stmmac: Enable timestamping interrupt on dwmac1000

The default configuration for the interrupts on dwmac1000 have the
timestamping interrupt masked. Now that the timestamping has been
adapted to dwmac1000, enable the timestamping interrupt on these
platforms.

On dwmac1000, the external snapshot interrupt is configured through a
dedicated bit, that is set as reserved on other dwmac variants. The
timestaming interrupt is acknowledged by reading the
GMAC3_X_TIMESTAMP_STATUS register.

Make sure that this interrupt is enabled when snapshot is enabled, and
masked when disabled.

Reviewed-by: Daniel Machon <daniel.machon@microchip.com>
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20241112170658.2388529-7-maxime.chevallier@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>