util-linux: Create u-a symlink for findfs utility

util-linux: Create u-a symlink for findfs utility

busybox also installs findfs but into base_sbindir which works out to be
ok when sbindir != base_sbindir but with usrmerge distro feature enabled
this starts to cause trouble because busybox's postinst is trying to
create a symlink for findfs applet in base_sbindir which is same as
sbindir now and there already is binary from util-linux and image fails
to build

do_rootfs: Postinstall scriptlets of ['busybox'] have failed. If the intention is to defer them to first boot,
then please place them into pkg_postinst_ontarget:${PN} ().

The real reason is burried in do_rootfs logs

update-alternatives: Error: not linking /mnt/b/yoe/master/build/tmp/work/beaglebone-yoe-linux-gnueabi/yoe-sdk-image/1.0-r0/rootfs/usr/sbin/findfs to /usr/bin/busybox.suid since /mnt/b/yoe/master/build/tmp/work/beaglebone-yoe-linux-gnueabi/yoe-sdk-image/1.0-r0/rootfs/usr/sbin/findfs exists and is not a link

Creating proper u-a for findfs in util-linux fixes the issue

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>