src/poky:rpm: upgrade to 4.15.1

Drop patches that were merged upstream.

0001-mono-find-provides-requires-do-not-use-monodis-from-.patch
modifies a file that was removed upstream.

Add a 0001-rpmfc.c-do-not-run-file-classification-in-parallel.patch
as unfortunately the new parallel file classification feature from
upstream trips over somewhere in libmagic when inspected files are
compressed:
rpm-software-management/rpm#756

(From OE-Core rev: 67257ca87c6fa8e6050a20ecea50daf834c7e869)

Signed-off-by: Alexander Kanavin <alex.kanavin@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>