[bsp][stm32f746-disco] Add support of IAR tool chain

[bsp]add stm32f4xx bsp rtc driver

1. Add IAR project template and link scripts. Add missing CXX configuration for IAR tool chain in rtconfg.py.
2. Modify all link scripts, Using ITCM interface.(Changing flash start address from 0x0800_0000 to 0x0020_0000).

[libc][dlib] Add missing definition of mode_t

For using pthread with IAR tool chain

[bsp][stm32f746-Disco] Cleanup code

1. Using RT_USING_COMPONENTS_INIT and RT_USING_USER_MAIN
2. Cleanup code

code cleanup.

[DFS] fix the fd_put issue in mkdir and lseek error case.

[Kernel] change to open the console device and then set the console device.

in rt_console_set_device, open new device first and get the new device to _console_device.
我在编写程序时，在device驱动中打印log，但是使用rt_kprintf时，如果_console_device存在非空，那就执行驱动的write函数，但是这是device还没有初始化成功，但是已经提前给_console_device赋值，导致了程序无故fault，以上述修改可避开这样的矛盾。

[DeviceDrivers] Add hardware timer framework

[BSP] Add tms320dm365