accel/tcg: remove link between guest ram and TCG cache size

accel/tcg: remove link between guest ram and TCG cache size

Basing the TB cache size on the ram_size was always a little heuristic
and was broken by a1b18df9a4 which caused ram_size not to be fully
realised at the time we initialise the TCG translation cache.

The current DEFAULT_CODE_GEN_BUFFER_SIZE may still be a little small
but follow-up patches will address that.

Fixes: a1b18df9a4
Cc: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Niek Linnenbank <nieklinnenbank@gmail.com>
Message-Id: <20200228192415.19867-3-alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>