Add PMD parameter that allows one to select only subset of available
GPIOs.
This might be useful in cases where some GPIOs are already reserved yet
still available for userspace access but particular app should not touch
them.
Signed-off-by: Tomasz Duszynski <tduszynski@marvell.com>
Reviewed-by: Jerin Jacob <jerinj@marvell.com>