Patch to support Amlogic uart lower speeds

[john-feith.com]

Summary

This patch adds support for the extended baud rate register
available on the aml8726-m6 (and later) SoC which allows for
lower speeds.

Test Plan

Smoke tested on the ODROID-C1 at 110, 150, 300, 600, 1200,
38400, and 115200 baud.

[ganbold]

Other than style in one place it seems ok.

sys/arm/amlogic/aml8726/uart_dev_aml8726.c

158

I'm not good at style(9), but I'd get one tab (4 spaces) from if column. Actually style(9) recommends:
...
Indentation is an 8 character tab. Second level indents are four spaces.
...

[john-feith.com]

I've reformatted the line in question.