target/riscv: Remove experimental prefix from "B" extension

This extension has now been ratified:
https://jira.riscv.org/browse/RVS-2006 so the "x-" prefix can be
removed.

Since this is now a ratified extension add it to the list of extensions
included in the "max" CPU variant.

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
Message-ID: <20240514110217.22516-1-rbradford@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu.c

@@ -1400,7 +1400,7 @@ static const MISAExtInfo misa_ext_info_arr[] = {
     MISA_EXT_INFO(RVJ, "x-j", "Dynamic translated languages"),
     MISA_EXT_INFO(RVV, "v", "Vector operations"),
     MISA_EXT_INFO(RVG, "g", "General purpose (IMAFD_Zicsr_Zifencei)"),
-    MISA_EXT_INFO(RVB, "x-b", "Bit manipulation (Zba_Zbb_Zbs)")
+    MISA_EXT_INFO(RVB, "b", "Bit manipulation (Zba_Zbb_Zbs)")
 };
 
 static void riscv_cpu_validate_misa_mxl(RISCVCPUClass *mcc)

target/riscv/tcg/tcg-cpu.c

@@ -1301,7 +1301,7 @@ static void riscv_init_max_cpu_extensions(Object *obj)
     const RISCVCPUMultiExtConfig *prop;
 
     /* Enable RVG, RVJ and RVV that are disabled by default */
-    riscv_cpu_set_misa_ext(env, env->misa_ext | RVG | RVJ | RVV);
+    riscv_cpu_set_misa_ext(env, env->misa_ext | RVB | RVG | RVJ | RVV);
 
     for (prop = riscv_cpu_extensions; prop && prop->name; prop++) {
         isa_ext_update_enabled(cpu, prop->offset, true);