can: mcp251xfd: rename all user facing strings 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 user facing strings from
"mcp25xxfd" to "mcp251xfd" and "MCP25XXFD" to "MCP251XFD", including:
- kconfig symbols
- name of kernel module
- DT and SPI compatible

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

Link: https://lore.kernel.org/r/20200930091424.792165-9-mkl@pengutronix.de
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>