Update i2c_core.c

修复I2C读写函数，I2C传输失败时返回成功的问题

components/drivers/i2c/i2c_core.c

@@ -93,7 +93,7 @@ rt_size_t rt_i2c_master_send(struct rt_i2c_bus_device *bus,
                              const rt_uint8_t         *buf,
                              rt_uint32_t               count)
 {
-    rt_size_t ret;
+    rt_err_t ret;
     struct rt_i2c_msg msg;
 
     msg.addr  = addr;
@@ -112,7 +112,7 @@ rt_size_t rt_i2c_master_recv(struct rt_i2c_bus_device *bus,
                              rt_uint8_t               *buf,
                              rt_uint32_t               count)
 {
-    rt_size_t ret;
+    rt_err_t ret;
     struct rt_i2c_msg msg;
     RT_ASSERT(bus != RT_NULL);