IOPBios: use memcpy read/write functions instead of 8 bit loops

[F0bes]

Description of Changes

Instead of moving data in 8-bit loops, use safeiopmem(read/write) functions which use an underlying memcpy.

Rationale behind Changes

Minor performance increase in medium to large ioman I/O

When reading hostfs on master, our hottest point (besides the EE JIT) was the recClearIOP function called by each iopMemWrite8.
With this PR we now see faster execution times (~8.5%) with my hostfs bench-marking tool, and more CPU time on read().

Suggested Testing Steps

See if games and homebrew that uses HostFS still work.