include/linux/pid.h: remove next_pidmap() declaration

Commit 95846ecf ("pid: replace pid bitmap implementation with IDR
API") removed next_pidmap() but left its declaration.

Remove it.  No functional change.

Link: http://lkml.kernel.org/r/20190213113736.21922-1-namit@vmware.com


Signed-off-by: Nadav Amit <namit@vmware.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Gargi Sharma <gs051095@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>