chrt: Add support for (GRUB) bandwidth reclaim

chrt: Add support for (GRUB) bandwidth reclaim

The SCHED_DEADLINE policy supports the (GRUB) Greedy Reclamation
of Unused Bandwidth algorithm. This allows tasks to reclaim
bandwidth that are left over by other deadline tasks that finish
their work early, or voluntarily yield the cpu.

Currently, chrt has no way to set the SCHED_FLAG_RECLAIM bit in
the sched_flags field of the sched_attr structure.

Add -G/--reclaim-grub option to allow users to toggle this feature
using the deadline scheduling class.

[kzak@redhat.com: - add missing #ifdef SCHED_FLAG_RECLAIM guards
                  - add comments to #else/#endif for SCHED_DEADLINE block]
Signed-off-by: Furkan Caliskan <frn1furkan10@gmail.com>