Fix build warning/error about converting a constant to a boolean (#42389)

Fix build warning/error about converting a constant to a boolean (#42389)

On Fedora 32 with Clang 10, I get this warning/error when building
coreclr:

    /home/omajid/devel/dotnet/runtime/src/coreclr/src/jit/emitarm.cpp:5553:31: error: converting the enum constant to a boolean [-Werror,-Wint-in-bool-context]
            assert(ins == INS_cbz || INS_cbnz);
                                  ^

This looks like a bug that should be fixed: ins should be compared with
the constant on both sides of the boolean operator. Otherwise the
conditional can always evaluate to true.