microchip: lan865x: fix missing Timer Increment config for Rev.B0/B1

microchip: lan865x: fix missing Timer Increment config for Rev.B0/B1

Fix missing configuration for LAN865x silicon revisions B0 and B1 as per
Microchip Application Note AN1760 (Rev F, June 2024).

The Timer Increment register was not being set, which is required for
accurate timestamping. As per the application note, configure the MAC to
set timestamping at the end of the Start of Frame Delimiter (SFD), and
set the Timer Increment register to 40 ns (corresponding to a 25 MHz
internal clock).

Link: https://www.microchip.com/en-us/application-notes/an1760
Fixes: 5cd2340cb6a3 ("microchip: lan865x: add driver support for Microchip's LAN865X MAC-PHY")
Signed-off-by: Parthiban Veerasooran <parthiban.veerasooran@microchip.com>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://patch.msgid.link/20250818060514.52795-3-parthiban.veerasooran@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>