dt-bindings: mfd: stm32-timers: Move fixed string node names under 'properties'

Fixed string node names should be under 'properties' rather than
'patternProperties'. Additionally, without beginning and end of line
anchors, any prefix or suffix is allowed on the specified node name.

Move the stm32 timers 'counter' and 'timer' nodes to the 'properties'
section.

Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20220706211934.567432-1-robh@kernel.org