ENGR00274473-1 regulator: add more notifier events

ENGR00274473-1 regulator: add more notifier events

Some hardware modules need strict flows according
to regulator's enable/disable, such as for i.MX6
SOC's PU regulator, there is another power gate
in GPC module, it needs to disable PU modules' clock
before PU regulator is disabled and need to enable
clock right after PU regulator is enabled, then it
can do GPC's power gate operation.

So we need to add REGULATOR_EVENT_PRE_DISABLE and
REGULATOR_EVENT_ENABLE for regulator's notifier events.

Signed-off-by: Anson Huang <b20788@freescale.com>