gpio: mvmfp: support newer MFP bit definitions

1. The bits 11..10 for mfp driver strength is only valid for
aspen and old xscale family, for newer Marvell chip, this range
has been moved to 12..11.
2. add sleep bit support

Signed-off-by: Xiang Wang <wangx@marvell.com>
[robh: rebase to current mainline]
Signed-off-by: Rob Herring <robh@kernel.org>
2 files changed