input: touchscreen: ft8719_spi_c3j: Fix Wfortify-source warnings

drivers/input/touchscreen/ft8719_spi_c3j/focaltech_ex_fun.c:165:3:
warning: 'snprintf' size argument is too large; destination buffer
has size 25, but size argument is 4096 [-Wfortify-source]
  165 |                 snprintf(tmp, PAGE_SIZE, "%s", writebuf + 1);
      |                 ^
drivers/input/touchscreen/ft8719_spi_c3j/focaltech_ex_fun.c:887:2:
warning: 'snprintf' size argument is too large; destination buffer
has size 128, but size argument is 4096 [-Wfortify-source]
  887 |         snprintf(fwname, PAGE_SIZE, "%s", buf);
      |         ^
drivers/input/touchscreen/ft8719_spi_c3j/focaltech_ex_fun.c:917:2:
warning: 'snprintf' size argument is too large; destination buffer
has size 128, but size argument is 4096 [-Wfortify-source]
  917 |         snprintf(fwname, PAGE_SIZE, "%s", buf);
      |         ^
drivers/input/touchscreen/ft8719_spi_c3j/focaltech_test/focaltech_test_ini.c:739:4:
warning: 'snprintf' size argument is too large; destination buffer
has size 50, but size argument is 512 [-Wfortify-source]
  739 |                         snprintf(str, MAX_KEYWORD_VALUE_LEN, "InvalidNode[%d][%d]", i, j);
      |                         ^
drivers/input/touchscreen/ft8719_spi_c3j/focaltech_test/focaltech_test_ini.c:752:4:
warning: 'snprintf' size argument is too large; destination buffer
has size 50, but size argument is 512 [-Wfortify-source]
  752 |                         snprintf(str, MAX_KEYWORD_VALUE_LEN, "InvalidNodeS[%d][%d]", i, j);
      |                         ^

Change-Id: I7445a37c618e83209ec2b6cf2c00b64bd77b5f0b