regulator: qpnp-labibb: Allow 0 ms for IBB PWRUP_DLY1 and PWRDN_DLY2

Currently, IBB PWRUP_DLY1 and PWRDN_DLY2 settings are configured
only for values greater than 0. However, 0 ms (no delay) can be
allowed by disabling EN_PWRUP_DLY1 or EN_PWRDN_DLY2 bits. Add
support to allow this configuration.

CRs-Fixed: 2125062
Change-Id: I8ef3b5522b8d4db6befb3fb1c2e58ea24c0f5ea0
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>