uart_dev_ns8250 now relies on compatible property instead of additional
'busy-detect' cell. All drivers with compatible = "snps,dw-apb-uart" have
busy detection turned on. DTS files of devices affected by the change
were modified and 'busy-detect' property was removed.

Reviewed by:    andrew, ian, imp
Obtained from:  Semihalf
Sponsored by:   Stormshield
Submitted by:   Bartosz Szczepanek <bsz@semihalf.com>
Differential revision:  https://reviews.freebsd.org/D4218