sched: Remove rq->avg_load_per_tas.

Change-Id: I435716b938104f32e76d54ed7cfc6c510df2b5cc
timekeeping: fix 32-bit overflow in get_monotonic_boottime

get_monotonic_boottime adds three nanonsecond values stored
in longs, followed by an s64.  If the long values are all
close to 1e9 the first three additions can overflow and
become negative when added to the s64.  Cast the first
value to s64 so that all additions are 64 bit.

Change-Id: I6834d87babaa0dfc1d89b14d997e49e4d7442532