can: mcp251xfd: rename all remaining occurrence to mcp251xfd

In [1] Geert noted that the autodetect compatible for the mcp25xxfd driver,
which is "microchip,mcp25xxfd" might be too generic and overlap with upcoming,
but incompatible chips.

In the previous patch the autodetect DT compatbile has been renamed to
"microchip,mcp251xfd", this patch changes all non user facing occurrence of
"mcp25xxfd" to "mcp251xfd" and "MCP25XXFD" to "MCP251XFD".

[1] http://lore.kernel.org/r/CAMuHMdVkwGjr6dJuMyhQNqFoJqbh6Ec5V2b5LenCshwpM2SDsQ@mail.gmail.com

Link: https://lore.kernel.org/r/20200930091424.792165-10-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>