riscv: add ISA extension parsing for Ztso

Add support to parse the Ztso string in the riscv,isa string. The
bindings already supports it but not the ISA parsing code.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Link: https://lore.kernel.org/r/20231220155723.684081-2-cleger@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: clementleger

arch/riscv/include/asm/hwcap.h

@@ -84,6 +84,7 @@
 #define RISCV_ISA_EXT_ZVFH		69
 #define RISCV_ISA_EXT_ZVFHMIN		70
 #define RISCV_ISA_EXT_ZFA		71
+#define RISCV_ISA_EXT_ZTSO		72
 
 #define RISCV_ISA_EXT_MAX		128
 #define RISCV_ISA_EXT_INVALID		U32_MAX

arch/riscv/kernel/cpufeature.c

@@ -279,6 +279,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
 	__RISCV_ISA_EXT_DATA(zkt, RISCV_ISA_EXT_ZKT),
 	__RISCV_ISA_EXT_DATA(zksed, RISCV_ISA_EXT_ZKSED),
 	__RISCV_ISA_EXT_DATA(zksh, RISCV_ISA_EXT_ZKSH),
+	__RISCV_ISA_EXT_DATA(ztso, RISCV_ISA_EXT_ZTSO),
 	__RISCV_ISA_EXT_SUPERSET(zvbb, RISCV_ISA_EXT_ZVBB, riscv_zvbb_exts),
 	__RISCV_ISA_EXT_DATA(zvbc, RISCV_ISA_EXT_ZVBC),
 	__RISCV_ISA_EXT_DATA(zvfh, RISCV_ISA_EXT_ZVFH),