drivers: net: lan865x: Disable protected transmission mode before reset

The LAN865x device after HW reset supports only the non-protected control
transmission mode. When it is reset alone - without resetting already
configured HOST system - one must assure that in HOST's OA TC6 driver
the protection SPI transmission support is disabled.

Signed-off-by: Lukasz Majewski <lukma@denx.de>