net: enetc: separate 64-bit counters from enetc_port_counters

net: enetc: separate 64-bit counters from enetc_port_counters

Some counters in enetc_port_counters are 32-bit registers, and some are
64-bit registers. But in the current driver, they are all read through
enetc_port_rd(), which can only read a 32-bit value. Therefore, separate
64-bit counters (enetc_pm_counters) from enetc_port_counters and use
enetc_port_rd64() to read the 64-bit statistics.

Signed-off-by: Wei Fang <wei.fang@nxp.com>
Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250627021108.3359642-3-wei.fang@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>