zd1211rw: Prefer pr_err over printk error msg

In zd_usb.c usb_init we can prefer pr_err() over printk KERN_ERR
log level.

Signed-off-by: Saurav Girepunje <saurav.girepunje@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20210506044838.GA7260@user