DFS: Allow switch to DFS channel after radar detection in ETSI

DFS: Allow switch to DFS channel after radar detection in ETSI

This is to comply with uniform spreading requirement for ETSI domain
(section 4.7.2.7 in EN 301 893 - V1.8.1). ETSI uniform spreading
requires equal probability for the usable channels. The previous channel
selection logic after a radar detection did not fully comply with the
uniform spreading requirement for the domain by ignoring DFS channels.
Consider DFS channels also during channel selection when the current DFS
domain is ETSI.

Signed-off-by: Vasanthakumar Thiagarajan <vthiagar@qti.qualcomm.com>