target/sparc: fake UltraSPARC T1 PCR and PIC registers

target/sparc: fake UltraSPARC T1 PCR and PIC registers

Fake access to
   PCR Performance Control Register
and
   PIC Performance Instrumentation Counter.

Ignore writes in privileged mode, and return 0 on reads.

This allows booting Tribblix, MilaX and v9os under Niagara target.

Signed-off-by: Artyom Tarasenko <atar4qemu@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20250209211248.50383-1-atar4qemu@gmail.com>