spi ASYNC requires use of -Wno-reinterpret-alignment

[ed-xmos]

It uses movable pointers and re-casts 8b to 32b. The original author wrote the compiler so we believe this is OK but it is not ideal however this code is deeply connected to the use of interfaces.

[ed-xmos]

We have not received any reported issues on this also. Without use of a memcpy which would adversely affect the performance on the async implementation, I cannot see an easy way to fix this. The use of movable pointers is required for the performance of this implementation and removes the remote reference compiler issue when accessing arrays across interface. Perhaps a test to check this (passing a non-aligned char array) would be helpful.