ANDROID: sched: add missing data type for cpu variable

While bringing in a change from older Kernel, commit 3adfd8e3
("ANDROID: sched: avoid placing RT threads on cores handling softirqs")
missed to add data type for cpu variable. Fix it by adding data type.

Bug: 168521633
Change-Id: I4cd3d0b68b5962004f295ce8d07546b2067bc728
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>