trace/sched: use proper specifier to avoid compilation errors

WALT utilization is u32 type. But the sched_load_se trace point
incorrectly uses %lu as its specifier, this results in a compilation
failure. Fix it by using %u specifier.

Change-Id: I2369c6bb79e09468301961a837875e7472148a83
Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>