rq->cpu only exists on CONFIG_SMP builds. PELT only needs to support
SMP-enabled builds, so guard rq_clock_task_mult with CONFIG_SMP to
support compilation of kernel without CONFIG_SMP enabled.
Change-Id: I7779f5b10b44757dfd4cbc159b6ae3f3f1ddf3e7
Fixes: 9377277724 ("ANDROID: sched: Introducing PELT multiplier")
Signed-off-by: Elliot Berman <quic_eberman@quicinc.com>