target/riscv: Add "pmu-mask" property to replace "pmu-num"

Using a mask instead of the number of PMU devices supports the accurate
emulation of platforms that have a discontinuous set of PMU counters.

The "pmu-num" property now generates a warning when used by the user on
the command line.

Rather than storing the value for "pmu-num" convert it directly to the
mask if it is specified (overwriting the default "pmu-mask" value)
likewise the value is calculated from the mask if the property value is
obtained.

In the unusual situation that both "pmu-mask" and "pmu-num" are provided
then then the order on the command line determines which takes
precedence (later overwriting earlier.)

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20231031154000.18134-5-rbradford@rivosinc.com>
[Changes by AF
 - Fixup ext_zihpm logic after rebase
]
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu_cfg.h

@@ -134,7 +134,7 @@ struct RISCVCPUConfig {
     bool ext_xtheadsync;
     bool ext_XVentanaCondOps;
 
-    uint8_t pmu_num;
+    uint32_t pmu_mask;
     char *priv_spec;
     char *user_spec;
     char *bext_spec;