Document FunC calling convention

[anton-trunov]

Is your feature request related to a problem? Please describe.

I believe the calling convention is not documented for FunC, which makes unclear how to write asm-functions, because assembly instructions expect certain TVM stack configurations (the order) which is important for multi-argument instructions.

Describe the solution you'd like

Document the order of function arguments and return values for tensor types.

Additional context

No response

[anton-trunov]

As far as I understand, FunC pushes function arguments in the order of function parameters declaration, so the stack order is reversed, i.e. for a function like the following one

int bin(int x, int y) { return y - x; }

the y is argument will be at the top of the TVM stack.