dt-bindings: Fix SPI and I2C bus node names in examples

SPI and I2C bus node names are expected to be "spi" or "i2c",
respectively, with nothing else, a unit-address, or a '-N' index. A
pattern of 'spi0' or 'i2c0' or similar has crept in. Fix all these
cases. Mostly scripted with the following commands:

git grep -l '\si2c[0-9] {' Documentation/devicetree/ | xargs sed -i -e 's/i2c[0-9] {/i2c {/'
git grep -l '\sspi[0-9] {' Documentation/devicetree/ | xargs sed -i -e 's/spi[0-9] {/spi {/'

With this, a few errors in examples were exposed and fixed.

Acked-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Marc Kleine-Budde <mkl@pengutronix.de> # for the microchip,mcp251xfd.yaml
Acked-by: Mark Brown <broonie@kernel.org>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Acked-by: Sebastian Reichel <sebastian.reichel@collabora.com> # for power-supply
Acked-by: Wolfram Sang <wsa@kernel.org>
Acked-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230228215433.3944508-1-robh@kernel.org


Signed-off-by: Rob Herring <robh@kernel.org>