spi: spi-sn-f-ospi: Make read-only array `width_available` static const

The `width_available` array is currently placed on the
`f_ospi_supports_op_width()` function's stack.

But the array is never modified. Make it `static const`. This makes the
code slightly smaller and more efficient.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20230528195830.164669-3-lars@metafoo.de


Signed-off-by: Mark Brown <broonie@kernel.org>