msm: krait-regulator: rename online to reg_en

The online variable is confusing, since it does not mean whether
the core is online or offline. It actually used to indicate whether
the regulator is enabled or disabled.
Change the variable name to indicate so.

Change-Id: I20c270162df57cf81c17e808d383880b5b2e4eef
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>