Bluetooth: controller: legacy: Fix channel map check regression

Fix channel map check regression introduced in
commit 2ca0b016 ("Bluetooth: controller: legacy:
Validate chan map and hop value"), that caused further
connection initiation to fail.

Relates to commit 94d5f085 ("Bluetooth: controller:
fixing error re. all zero chmap in conn-ind").

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>