RSP LDV/SDV Testing

[bryanperris]

This opcode pair is heavily involved in the RSP graphics ucode, so there should be tests for them.

[bryanperris]

Also need testing around the offset operand as it has to be clamped, graphics microcode won't work right unless clamping is done, to explain this better look at this line from cxd4's rsp source:
https://github.com/cxd4/rsp/blob/ee3cb4a9f6233a170db09729374c992ae8e30141/su.c#L1820