Transceiver52M: Allow disabling of energy detector

The adaptive energy threshold gating suffers a near-far problem
at certain gain levels. This is due to exponential threshold
raising, but linear decreases. A large signal level followed by
a period low signal level causes (comparatively) weak signals to
go undetected. Additionally, the algorithm performs differently
at multiple RF gain levels.

This patch switches solely to correlation based gating for burst
detection. At one SPS, the main computational load with this
approach is sub-sample width peak interpolation, which we disable
for intial detection.

This option is only enabled for one SPS.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Refactor RACH and normal burst detection

Both RACH and normal bursts are detected with the same approach of
midamble correlation combined with peak-to-average ratio. The
difference is the midamble placements and lengths. Thus, there is
no reason to have independent implementations.

This patch creates a common call burstDetect(), while leaving the
correlation window indexing in the original calls.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Disable fast peak detection

We are leaving the energy detector in place for now, so
run normal interpolating peak detection.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Reduce RACH and TSC correlation windows

Search 4 symbols before and 6 symbols after as the base
case.

Signed-off-by: Thomas Tsou <tom@tsou.cc>