Revert "power_control: BS power shall not be reduced on C0"
Revert "power_control: BS power shall not be reduced on C0"

This reverts commit cd30a40be15267c7257b733da4e9ffdf17f0614d.

As a part of SYS#4919 "BTS energy saving", we want to support
constrained (up to 6 dB) BS power control on BCCH carriers.

Change-Id: I0d2b48c4b2af2d8e94f4ad02fa4774dbd0a0a654
Related: SYS#4919

osmocom/osmo-bts,osmocom/osmo-bts,osmocom/osmo-bts