iwlwifi: mvm: return the actual error code when switch_vif_chanctx fails

We have code to recover and go back to the original channel context if
something fails in the middle of switch_vif_chanctx, but we return the
error code of the recover calls instead of the original code, so if
the recovery succeeds, we will return 0 (success).  Fix this by not
assigning the return value of the recovery calls to ret.

Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>