MFC r330358, r330360

r330358: Minor changes to wording.
r330360: Minor (mostly) wording changes.

MFC r330309:

[fdt_pinctrl] Add man pages for fdt_pinctrl driver

- Add fdt_pinctrl(4) with general information for the driver
- Add fdt_pinctrl(9) with fdt_pinctrl KPI description

Reviewed by: ian, manu, wblock
Differential Revision: https://reviews.freebsd.org/D14235