cmd: sbi: add support for Debug Trigger Extension

Detect and show if the SBI implements the Debug Trigger Extension.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index bf4c9af..d1113f3 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -33,6 +33,7 @@
 	SBI_EXT_CPPC = 0x43505043,
 	SBI_EXT_NACL = 0x4E41434C,
 	SBI_EXT_STA = 0x535441,
+	SBI_EXT_DBTR = 0x44425452,
 };
 
 enum sbi_ext_base_fid {