ipc: fix errors for GCC 8 support

ipc: fix errors for GCC 8 support

components/esp32/ipc.c: In function 'esp_ipc_init':
components/esp32/ipc.c:82:31: error: '%d' directive writing between 1 and 11 bytes into a region of size 5 [-Werror=format-overflow=]
         sprintf(task_name,"ipc%d",i);
                               ^~
components/esp32/ipc.c:82:27: note: directive argument in the range [-2147483648, 1]
         sprintf(task_name,"ipc%d",i);
                           ^~~~~~~
components/esp32/ipc.c:82:9: note: 'sprintf' output between 5 and 15 bytes into a destination of size 8
         sprintf(task_name,"ipc%d",i);
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~