In LiftoffCompiler::EmitTypeConversion() there is a DCHECK_EQ() where
one argument is implicitly converted to bool. This confuses MSVC, which
causes it to think the two arguments to DCHECK_EQ() do not have the same
type. Fix this with an explicit bool conversion!!

This does not affect the "v8_win64_msvc_compile_rel" bot, presumably
because it is a release bot with DCHECKs turned off.

Change-Id: I602ddae7a970e17388730e895eafd4ec78de7602
Reviewed-on: https://chromium-review.googlesource.com/1187702Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55381}