shell: implement echo command

Makefile

@@ -42,6 +42,7 @@ obj-y += source/ftl/map.o
 
 obj-y += source/shell/args.o
 obj-y += source/shell/cmd.o
+obj-y += source/shell/echo.o
 obj-y += source/shell/flash.o
 obj-y += source/shell/ftl.o
 obj-y += source/shell/mufs.o

include/shell/echo.h

@@ -0,0 +1,3 @@
+#pragma once
+
+void shell_echo(struct console *con, const char **argv, size_t argc);

source/shell/echo.c

@@ -0,0 +1,15 @@
+#include <stdio.h>
+
+#include <console.h>
+
+#include <shell/echo.h>
+
+void shell_echo(struct console *con, const char **argv, size_t argc)
+{
+	if (argc < 1)
+		return;
+
+	fprintf(con->fp, "%s\n", argv[0]);
+}
+
+