modules: canopennode: can_get_max_filters() is optional
modules: canopennode: can_get_max_filters() is optional

Support for the can_get_max_filters() API function is optional and may
not be supported by all drivers.

The check for an adequate amount of filters is just there in order to
fail early. If the driver does not support can_get_max_filters(),
reporting of a failure will be delayed until a filter addition fails.

Signed-off-by: Henrik Brix Andersen <24a3f13c22635bab658e39fc5f1e63c575328aae@vestas.com>

finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr