Check for sudo in Raspberry/examples/main.c

[abhillman]

这将帮助用户避免 segfault / this will help users avoid segfaults.

---

Before:

$ ./epd -2.51 0
/***********************************/ 
bcm2835 init success !!! 
Segmentation fault
$ echo $?
139

After:

$ sudo ./epd -2.51 0
/***********************************/ 
bcm2835 init success !!! 
/***********************************/ 
VCOM value:2510
Display mode:0
...
$ echo $?
0

cc/ @shhds @waveshare