[16-bit Multiplayer]: SIOCNT[7] should remain set until the master responds

[afska]

LinkRawCable_demo.zip

When using this ROM, the slave sets the data, sets bit 7 of SIOCNT, and then it waits until the bit is unset to get the response.

• On hardware, the bit is only unset after the master also sends.
  

• On mGBA 0.10.2, the bit is immediately set to zero, resulting in the return of old data
  

Source code of the ROM:
https://github.com/afska/gba-link-connection/blob/e04a7356ee28ba6a336f9ce1b791dc1611c92942/lib/LinkRawCable.hpp
https://github.com/afska/gba-link-connection/blob/e04a7356ee28ba6a336f9ce1b791dc1611c92942/examples/LinkRawCable_demo/src/main.cpp

[Testsr]

Confirmed on 0.10.3.