testing: add unistd.h for drivertest_touchpanel.c

Add unistd.h header file to drivertest_touchpanel.c to fix missing
sleep/usleep function declarations in touchpanel driver tests.

Signed-off-by: tengshuangshuang <tengshuangshuang@xiaomi.com>

testing/drivers/drivertest/drivertest_touchpanel.c

@@ -37,6 +37,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include <malloc.h>
 #include <string.h>
 #include <fcntl.h>