mfd: tps6591x: Implement proper power off sequence.

Implementing proper power off sequence.

bug 955418

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
(cherry picked from commit c5211e853cbb31feecfdf9a748846467dacec608)

Change-Id: Id3efaebefbcbb1dee85bb47b56b20b9b6358f421
Reviewed-on: http://mcrd1-5.corpnet.asus/code-review/master/56914
Reviewed-by: Singhome Lee <singhome_lee@asus.com>
Tested-by: Singhome Lee <singhome_lee@asus.com>
mfd: tps6591x: Avoid possible race condition

Add a delay to reflect regulator changes in HW

bug 955418

Change-Id: Id9b846b2a4d158b81c067c1e948712bc8a103e11
Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Reviewed-on: http://mcrd1-5.corpnet.asus/code-review/master/56915
Reviewed-by: Singhome Lee <singhome_lee@asus.com>
Tested-by: Singhome Lee <singhome_lee@asus.com>