wifi: iwlwifi: dvm: Remove unused iwl_rx_ant_restriction

iwl_rx_ant_restriction() was added in 2009 by
commit 46f9381a ("iwlwifi: Thermal Throttling Management - part 2")
but never used.

Remove it.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://patch.msgid.link/20241223013202.340180-2-linux@treblig.org