regulator: leave one item to record whether regulator is enabled

The items "disabled" and "enabled" are a little redundant, since only one
of them would be set to record if the regulator device should keep on
or be switched to off in suspend states.

So in this patch, the "disabled" was removed, only leave the "enabled":
  - enabled == 1 for regulator-on-in-suspend
  - enabled == 0 for regulator-off-in-suspend
  - enabled == -1 means do nothing when entering suspend mode.

Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>