mdadm: fix util-linux ptest dependency

mdadm: fix util-linux ptest dependency

Trying to run mdadm-ptest in a core-image-minimal build will result in:
root@qemux86-64:~# ptest-runner mdadm
START: ptest-runner
BEGIN: /usr/lib/mdadm/ptest
which: no lsblk in (/usr/local/bin:/usr/bin:/bin:/usr/local/sbin:/usr/sbin:/sbin)
lsblk command not found!
DURATION: 0
END: /usr/lib/mdadm/ptest
2023-06-28T10:14
STOP: ptest-runner
TOTAL: 1 FAIL: 0

Remove util-linux from RRECOMMENDS and only add util-linux-lsblk and
util-linux-losetup to RDEPENDS.

Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>