intel/fs: Define is_payload() method of the IR instruction class.

This is required because SEND message payload sources are fetched
asynchronously by the hardware, which can lead to WaR data corruption
on Gen12+ platforms if not handled specially by the compiler to
guarantee proper synchronization.

Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/intel/compiler/brw_ir_fs.h

@@ -348,6 +348,7 @@ public:
    void resize_sources(uint8_t num_sources);
 
    bool is_send_from_grf() const;
+   bool is_payload(unsigned arg) const;
    bool is_partial_write() const;
    bool is_copy_payload(const brw::simple_allocator &grf_alloc) const;
    unsigned components_read(unsigned i) const;