pinctrl: Proofreading and updating the documentation (part 2)

Do the following:
- update the "Definitions" style in two sections
- don't use "I" for technical documentation
- inline the remaining (variables, function names, file paths)

Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>