x86_64: fix @splat typo

Author: jacobly0

src/arch/x86_64/CodeGen.zig

@@ -165321,7 +165321,7 @@ fn genBody(cg: *CodeGen, body: []const Air.Inst.Index) InnerError!void {
                     .dst_temps = .{ .mem, .unused },
                     .each = .{ .once = &.{
                         .{ ._, ._, .mov, .tmp0d, .sia(-16, .dst0, .add_size), ._, ._ },
-                        .{ ._, .v_ps, .shuf, .tmp1x, .tmp1x, .src0x, .ui(0b00_00_00_00) },
+                        .{ ._, .v_ps, .shuf, .tmp1x, .src0x, .src0x, .ui(0b00_00_00_00) },
                         .{ .@"0:", .v_ps, .mova, .memi(.dst0x, .tmp0), .tmp1x, ._, ._ },
                         .{ ._, ._, .sub, .tmp0d, .si(16), ._, ._ },
                         .{ ._, ._nb, .j, .@"0b", ._, ._, ._ },