sched: use wake_q length only when WALT is enabled

Upstream commit aa8b37ba ("FROMLIST: sched/fair: Use wake_q
length as a hint for wake_wide") that is being carried in msm-5.4
kernel caused CRC checks failures when GKI boot image is used for
verification as the commit adds extra argument to select_task_rq().
Fix this issue by wrapping extra argument under CONFIG_SCHED_WALT.

Change-Id: Ie41a36a334efbcd2030f7c3caee31883ee84718e
Signed-off-by: Jeevan Shriram <jshriram@codeaurora.org>