This fixes undefined behavior introduced by extracting the const call
descriptor of a call node as non-const. Such an implicit cast between
constness is not safe and should be avoided.

R=ahaas@chromium.org
TEST=unittests/Int64LoweringTest.CallI64Parameter
BUG=v8:4924
LOG=n

Review URL: https://codereview.chromium.org/1900563002

Cr-Commit-Position: refs/heads/master@{#35569}