With COMPILE_TEST recently enabled, 0-day reports a warning:

drivers/watchdog/stm32_iwdg.c:215:34: warning: 'stm32_iwdg_of_match' defined but not used [-Wunused-const-variable=]

As STM32 platforms are always used with DT, drop the of_match_ptr().
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202308211837.4VBSUAtZ-lkp@intel.com/Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230823151059.2356881-1-robh@kernel.orgSigned-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>