MIPS: generic/ip32: io: fix __mem_ioswabq()

*readq() family operates with u64 arguments, so they need 64-bit
byteswaps.
Correct macros for Generic MIPS and IP-32 to match other machines'
implementations.

Signed-off-by: Alexander Lobakin <alobakin@pm.me>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>