regulator: twl: fix twl6030 regulator is_enabled

With TWL6030, it is not enough to ensure that the regulator is the
group of P1 group (CPU/Linux), but we need to check the state as far
as APP is concerned as well.

Split the current is_enabled to 6030 and 4030 specific ones. This
split impacts few macros and variables as well, but sets up the
stage for further fixes to set_mode and get_status in subsequent
patches.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Saquib Herman <saquib@ti.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@vega.(none)>