pinctrl: bcm: cleanup Broadcom license headers

Use consistent license headers for Broadcom files by
placing additional comments outside of standard legal header.

Also, update legal header to 2017 format as "Broadcom Corporation"
has changed to "Broadcom".

Signed-off-by: Scott Branden <scott.branden@broadcom.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>