nimble/phy/nrf: Fix setting -3dBm power on nRF5340
nimble/phy/nrf: Fix setting -3dBm power on nRF5340

There was a typo which would result in -4 dBm being set instead.

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble