dts: arm: nxp: lpc55sxx: reduce LPC MCAN RAM usage

Reduce the default RAM usage for the NXP LPC MCAN CAN controller driver by
reducing the number of RX buffers, TX buffers, and filter elements.

The LPC MCAN uses regular SRAM as backend and the default configuration
causes SRAM overflows for many CAN tests.

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