scripts/update-linux-headers: Handle __aligned_u64

scripts/update-linux-headers: Handle __aligned_u64

We'll currently replace any 'u64' with a 'uint64_t' including when
it's embedded in an '__aligned_u64', creating a '__aligned_uint64_t'
which doesn't exist. We need to instead expand out the kernel's
definition of __aligned_u64:
   #define __aligned_u64 __u64 __attribute__((aligned(8)))
before we convert the __u64 to uint64_t.

Signed-off-by: Peter Maydell <[email protected]>
Message-Id: <20180525132755[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>