mac_newworld: always enable disable_direct_reg3_writes for ADB machines

mac_newworld: always enable disable_direct_reg3_writes for ADB machines

Commit 84051eb400 "adb: add property to disable direct reg 3 writes" added a
workaround for MacOS 9 incorrectly setting the mouse address during boot of
PMU machines.

Further testing has shown that since fb6649f172 "adb: fix read reg 3 byte
ordering" this can still sometimes happen with the CUDA mac99 machine,
so let's enable this workaround for all New World machines using ADB for now.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>