The addend in `emac_hal_ptp_start()` was derived from the floating-point
`config->ptp_req_accuracy_ns` instead of the integer `base_increment`
register that actually drives the sub-second update. The cast to
`uint8_t` loses the fractional part, so the un-corrected addend leaves
the PTP clock running off-rate.
Example: with a 40 MHz XTAL and the default `req_accuracy_ns = 40`,
`base_increment` rounds 85.899 up to 86, leaving the clock +1170 ppm
fast — well outside the IEEE 802.1AS neighborRateRatio limit (~±200
ppm), so strict-1AS bridges refuse asCapable.
Compute the addend from the stored `base_increment` for both rollover
modes: `addend = 2^32 * clk_period_ns / increment_ns`.
Measured on ESP32-P4: neighborRateRatio drops from +1147.5 ppm to
+4.2 ppm, and asCapable is granted.
Co-authored-by: Ondrej Kosta <panzer412@gmail.com>
