Use the bb.utils.sha* utilities to hash files since they are much faster
than the loops we were rolling ourselves
(From OE-Core rev: a6d9de5350937c7e25899491db59f473345f0b69)
Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>