lib: sbi: Add Zkr in hart extensions

- Add Zkr as extension in sbi_hart_extensions enum
- Return "zkr" string for Zkr extension from sbi_hart_extension_id2string

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Anup Patel <anup@brainfault.org>

lib/sbi/sbi_hart.c

@@ -678,6 +678,9 @@ static inline char *sbi_hart_extension_id2string(int ext)
 	case SBI_HART_EXT_ZIHPM:
 		estr = "zihpm";
 		break;
+	case SBI_HART_EXT_ZKR:
+		estr = "zkr";
+		break;
 	case SBI_HART_EXT_SMEPMP:
 		estr = "smepmp";
 		break;