iwl4965: drop a lone pr_err()

iwl4965_rate_control_register() prints a message at KERN_ERR level. It
looks like it's just a debugging message, so pr_err() seems to be
overdone. But none of the similar functions in drivers/net/wireless
print a message, so let's just drop it.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: John W. Linville <linville@tuxdriver.com>