Add the ELF definition for the powerpc64 architecture when building
with musl as libc.
(From OE-Core rev: 2c09ab40fd92a49d16352639331db9c7e5171515)
Signed-off-by: Serhey Popovych <serhe.popovych@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>