leds: qpnp-wled: add delay after LAB enable

If IBB bias active is enabled then add delay after LAB
enable. It makes sure LAB is powered up before IBB.

Change-Id: I7d2f8ac839140852fe8f828aa4707974f11c113b
Signed-off-by: Mohan Pallaka <mpallaka@codeaurora.org>