target/riscv: detailed error messages for cases when resume operation…

… fails

This change aims to provide more context in case if resume operation
fails. Before the change messages were quite confusing.

src/target/riscv/riscv-013.c

@@ -5418,16 +5418,22 @@ static int riscv013_step_or_resume_current_hart(struct target *target,
 		return ERROR_OK;
 	}
 
+	LOG_TARGET_ERROR(target, "unable to %s. dmstatus=0x%08x",
+		step ? "single-step" : "resume", dmstatus);
+
 	dm_write(target, DM_DMCONTROL, dmcontrol);
+	LOG_TARGET_ERROR(target, "  cancelling RESUMEREQ");
 
-	LOG_TARGET_ERROR(target, "unable to resume");
 	if (dmstatus_read(target, &dmstatus, true) != ERROR_OK)
 		return ERROR_FAIL;
-	LOG_TARGET_ERROR(target, "  dmstatus=0x%08x", dmstatus);
+
+	LOG_TARGET_ERROR(target, "  dmstatus after cancellation=0x%08x", dmstatus);
 
 	if (step) {
-		LOG_TARGET_ERROR(target, "  was stepping, halting");
+		LOG_TARGET_ERROR(target,
+			"  trying to restore from failed single-step, by requesting throw-away halt");
 		riscv_halt(target);
+		// TODO: returning ERROR_OK is questionable, this code needs to be revised
 		return ERROR_OK;
 	}