util-linux: fix alternatives setting for switch-root

util-linux: fix alternatives setting for switch-root

The alternative setting for switch_root belongs to the util-linux-switch-root
package instead of the util-linux package. Fix this problem to avoid
a dangling symlink:
   /usr/bin/switch_root-> /usr/bin/switch_root.util-linux
on target and in the sdk.

Signed-off-by: Randy MacLeod <Randy.MacLeod@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>