Fix last two functions in sys_math_atan

[mzxrules]

renamed them to ~~Math_Atan2S_Depr~~ Math_Atan2S_XY and ~~Math_Atan2F_Depr~~ Math_Atan2F_XY, as they use x,y argument ordering used in OoT, instead of the more standard y,x argument ordering.