cputlb: Byte swap memory transaction attribute

cputlb: Byte swap memory transaction attribute

Notice new attribute, byte swap, and force the transaction through the
memory slow path.

Required by architectures that can invert endianness of memory
transaction, e.g. SPARC64 has the Invert Endian TTE bit.

Suggested-by: Richard Henderson <[email protected]>
Signed-off-by: Tony Nguyen <[email protected]>
Reviewed-by: Richard Henderson <[email protected]>
Message-Id: <2a10a1f1c00a894af1212c8f68ef09c2966023c1.1566466906[email protected]>
Signed-off-by: Richard Henderson <[email protected]>