net: lan966x: Update lan966x_ptp_get_nominal_value

The clk_per_cfg register represents the value added to the system clock
for each clock cycle. The issue is that the default value is wrong,
meaning that in case the DUT was a grandmaster then everone in the
network was too slow. In case there was a grandmaster, then there is no
issue because the DUT will configure clk_per_cfg register based on the
master frequency.

Fixes: d0964594 ("net: lan966x: Add support for ptp clocks")
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/microchip/lan966x/lan966x_ptp.c

@@ -29,10 +29,10 @@ enum {
 
 static u64 lan966x_ptp_get_nominal_value(void)
 {
-	u64 res = 0x304d2df1;
-
-	res <<= 32;
-	return res;
+	/* This is the default value that for each system clock, the time of day
+	 * is increased. It has the format 5.59 nanosecond.
+	 */
+	return 0x304d4873ecade305;
 }
 
 int lan966x_ptp_hwtstamp_set(struct lan966x_port *port, struct ifreq *ifr)