Have gen_analyze_funcs mark the registers that are read by the
instruction.  We also mark the implicit reads using instruction
attributes.

Signed-off-by: Taylor Simpson <tsimpson@quicinc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230427230012.3800327-11-tsimpson@quicinc.com>