fixup: using rt_kprintf instead of libc API for kernel source

Signed-off-by: Shell <smokewood@qq.com>

bsp/allwinner/d1s/applications/main.c

@@ -12,7 +12,7 @@
 
 int main(void)
 {
-    printf("Hello RISC-V\n");
+    rt_kprintf("Hello RISC-V\n");
 
 #ifdef BSP_USING_LCD
     extern int rt_hw_lcd_init(void);