drivers: can: stm32h7: remove unused std/ext filter size Kconfig options

Remove the STM32H7 specific Kconfig overrides for setting the maximum
number of standard and extended CAN RX filters as they are unused.

The number of available standard and extended filter elements for Bosch
M_CAN can be configured via the devicetree.

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