pinctrl: bcm: pinctrl-bcm281xx: Demote obvious misuse of kerneldoc to standard comment blocks

There has been little to no attempt to document any of the demoted
structures here.  These are obviously not kerneldoc headers.

Fixes the following W=1 kernel build warning(s):

 drivers/pinctrl/bcm/pinctrl-bcm281xx.c:65: warning: cannot understand function prototype: 'enum bcm281xx_pin_type '
 drivers/pinctrl/bcm/pinctrl-bcm281xx.c:79: warning: cannot understand function prototype: 'struct bcm281xx_pin_function '
 drivers/pinctrl/bcm/pinctrl-bcm281xx.c:89: warning: cannot understand function prototype: 'struct bcm281xx_pinctrl_data '

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Scott Branden <scott.branden@broadcom.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Ray Jui <rjui@broadcom.com>
Cc: Scott Branden <sbranden@broadcom.com>
Cc: bcm-kernel-feedback-list@broadcom.com
Cc: YueHaibing <yuehaibing@huawei.com>
Link: https://lore.kernel.org/r/20200713144930.1034632-4-lee.jones@linaro.org


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>