kernel/range.c: subtract_range: fix the broken phrase issued by printk

Also replace deprecated printk(KERN_ERR...) with pr_err() as suggested
by Yinghai, attaching the function name to provide plenty info.

Signed-off-by: Lin Feng <linfeng@cn.fujitsu.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>