Use the cached pmc_ins_cnt value.  Unroll the loop over the
different PMC counters.  Treat the PMC4 run-latch specially.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220103224746.167831-3-danielhb413@gmail.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>