can: mcp251xfd: ring: change order of TX and RX FIFOs

can: mcp251xfd: ring: change order of TX and RX FIFOs

This patch actually changes the order of the TX and RX FIFOs.

This gives the opportunity to minimize the number of SPI transfers in
the IRQ handler. The read of the IRQ status register and RX FIFO
status registers can be combined into single SPI transfer. If the RX
ring uses FIFO 1, the overall length of the transfer is smaller than
in the original layout, where the RX FIFO comes after the TX FIFO.

Link: https://lore.kernel.org/all/20220217103826.2299157-5-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>