staging/frontier: fix checkpatch warnings

The below checkpatch warns was fixed,

drivers/staging/frontier/tranzport.c:356: WARNING: Prefer pr_err(... to printk(KERN_ERR, ...
drivers/staging/frontier/tranzport.c:523: WARNING: Prefer pr_err(... to printk(KERN_ERR, ...
drivers/staging/frontier/tranzport.c:696: WARNING: Prefer pr_err(... to printk(KERN_ERR, ...
drivers/staging/frontier/alphatrack.c:336: WARNING: Prefer pr_err(... to printk(KERN_ERR, ...
drivers/staging/frontier/alphatrack.c:497: WARNING: Prefer pr_err(... to printk(KERN_ERR, ...
drivers/staging/frontier/alphatrack.c:568: WARNING: Prefer pr_err(... to printk(KERN_ERR, ...

Signed-off-by: Toshiaki Yamane <yamanetoshi@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>