ath10k: refactor radar detection code

If 20MHz CAC completed successfully then
subsequent CAC with wider bandwidth (40Mhz, 80Mhz)
with identical control frequency did not start
monitor vdev making it impossible to detect any
radar pulses during intended CAC.

It also was incorrect to assume ath10k_config() will
be called after CAC is finished. Theoretically for
non-HT channels nothing changes between CAC and
start_ap() (albeit in practice this can be
different). The incorrect assumption led to CAC
not being stopped on non-HT chandefs leading to
all Rx being drooped making it impossible for
clients to associate.

While at it clean up the code a bit.

kvalo: separate WARN_ON() from the if statement

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>