dt-bindings: mfd: fix stm32 timers example

dt-bindings: mfd: fix stm32 timers example

The stm32 timers example name should match the pattern timer@. Also,
the example is based on stm32mp1 timer 2, so the identifier should be
'1' instead of '0' (e.g. timer 1).

Fixes: 3a71ab07967d ("dt-bindings: timer: Convert stm32 timer bindings to json-schema")
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>
Link: https://lore.kernel.org/r/1606913114-25693-1-git-send-email-fabrice.gasnier@foss.st.com
Signed-off-by: Rob Herring <robh@kernel.org>