regulator: tps6591x: delay for LDOs to stabilize

regulator: tps6591x: delay for LDOs to stabilize

after enabling any LDO/SM, there is a specific amount of delay
required before the regulator becomes stable.

Original-Change-Id: I7cce3d8aad8859af0cbda7e114850fc95fe34eea
Reviewed-on: http://git-master/r/30862
Reviewed-by: Laxman Dewangan <ldewangan@nvidia.com>
Reviewed-by: Varun Wadekar <vwadekar@nvidia.com>
Reviewed-by: Pritesh Raithatha <praithatha@nvidia.com>
Tested-by: Pritesh Raithatha <praithatha@nvidia.com>
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>
Reviewed-by: Mayuresh Kulkarni <mkulkarni@nvidia.com>
Rebase-Id: R5b213829fa0489c2d147df738d449863e4bf0d95