syscall-emul: Remove unused class and member

syscall-emul: Remove unused class and member

The WaitRec structure in the Process class is unnecessary. There
is a member declaration inside of the Process class, waitList,
that uses the WaitRec definition. However, waitList is unused so
they are both dead bits of code. This changeset removes both the
WaitRec struct and waitList member from Process.

Change-Id: Ia6ee7488b9f47fd0f0ae29c818fba6ea0710699c
Reviewed-on: https://gem5-review.googlesource.com/2262
Reviewed-by: Tony Gutierrez <anthony.gutierrez@amd.com>
Reviewed-by: Michael LeBeane <Michael.Lebeane@amd.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>