wifi: iwlwifi: rs-fw: break out for unsupported bandwidth

Currently the for loop runs also over unsupported bandwidth in the
command, shorten the path in case we don't support it.

Also use the right macro for setting BW20.

Signed-off-by: Mordechay Goodstein <mordechay.goodstein@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230305124407.0264ba9df63b.I6c7c9efc806e0ffb7cb3b6051b2d109646e8708c@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>