Revert "kernel/sched: Remove dl_boosted flag comment"

This reverts commit 0b02218d which is
commit 0e3872499de1a1230cef5221607d71aa09264bd5 upstream.

It is a comment change for a commit that will be reverted next in the
series that broke the abi, so revert this as well.

Bug: 161946584
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I8ee94098946dd322d5dcd05421ca253123677fde