aco/vn: remove instruction hash templates

This reuses the instruction data size helper used for creating instruction.
It also removes the hashing of the aco::spans used for operands and definitions,
which was redundant with hash finalization.

Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28527>

src/amd/compiler/aco_ir.cpp

@@ -1392,7 +1392,7 @@ Instruction::isTrans() const noexcept
           instr_info.classes[(int)opcode] == instr_class::valu_double_transcendental;
 }
 
-static size_t
+size_t
 get_instr_data_size(Format format)
 {
    switch (format) {