can: mcp251xfd: ring: increase number of RX-FIFOs to 3 and increase max TX-FIFO depth to 16

This patch increases the number of RX-FIFOs to 3 and the max TX-FIFO
depth to 16. This leads to the following default ring configuration.

CAN-2.0 mode:

| FIFO setup: TEF:         0x400:  8*12 bytes =   96 bytes
| FIFO setup: RX-0: FIFO 1/0x460: 32*20 bytes =  640 bytes
| FIFO setup: RX-1: FIFO 2/0x6e0: 32*20 bytes =  640 bytes
| FIFO setup: RX-2: FIFO 3/0x960: 16*20 bytes =  320 bytes
| FIFO setup: TX:   FIFO 4/0xaa0:  8*16 bytes =  128 bytes
| FIFO setup: free:                              224 bytes

CAN-FD mode:

| FIFO setup: TEF:         0x400:  4*12 bytes =   48 bytes
| FIFO setup: RX-0: FIFO 1/0x430: 16*76 bytes = 1216 bytes
| FIFO setup: RX-1: FIFO 2/0x8f0:  4*76 bytes =  304 bytes
| FIFO setup: TX:   FIFO 3/0xa20:  4*72 bytes =  288 bytes
| FIFO setup: free:                              192 bytes

With the previously added ethtool ring configuration support the RAM
on the chip can now be runtime configure...