spi: SPI core CS delay fixes and additions

Merge series from Hector Martin <marcan@marcan.st>:

Commits f6c911f3 ("spi: dt-bindings: Introduce
spi-cs-setup-ns property") and 33a2fde5 ("spi: Introduce
spi-cs-setup-ns property") introduced a new property to represent the
CS setup delay in the device tree, but they have some issues:

- The property is only parsed as a 16-bit integer number of nanoseconds,
  which limits the maximum value to ~65us. This is not a reasonable
  upper limit, as some devices might need a lot more.
- The property name is inconsistent with other delay properties, which
  use a "*-delay-ns" naming scheme.
- Only the setup delay is introduced, but not the related hold and
  inactive delay times.

This series fixes the issues and adds support for the two missing
properties. Please pull in the first 3 patches as fixes for 6.2, to
avoid introducing a problematic DT API in this release. The last two
patches can wait until 6.3, though are probably harmless to throw in
as fixes too, since they're trivial.