idr: fix wrong kernel-doc

idr_get_new_above() and ida_get_new_above() return an id in the range of
@staring_id ... 0x7fffffff, not 0 ... 0x7fffffff.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>