Handle -inf for Torchscript of FX graphs

[anijain2305]

Repro

import torch
import torch.fx

x = torch.randn(4, 5)
mask = torch.randn(4, 5) > 0.5

def f(x, mask):
    # return x.masked_fill_(mask, 1.0) # PASSES
    return x.masked_fill_(mask, float("-inf"))

print(f(x, mask))

# Only fails when symbolic_trace
fx_mod = torch.fx.symbolic_trace(f)
scripted_f = torch.jit.script(fx_mod)
print(scripted_f(x, mask))

@eellison