arm64: dts: st: omit unused pinctrl groups from stm32mp25 dtb files

arm64: dts: st: omit unused pinctrl groups from stm32mp25 dtb files

stm32mp25-pinctrl.dtsi gathers all pinctrl groups from current and future
STM32MP25-based boards. Some groups may remain unused by any board,
resulting in wasted binary space.
Adding /omit-if-no-ref/ to the groups will remove unused groups from the
device tree blobs.

Use the following regex to update the file:
's/^\t[^:]\+: [^ ]\+ {$/\t\/omit-if-no-ref\/\n&/'
Also, merge the duplicated pinctrl_z node.

Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://lore.kernel.org/r/20260311-mp25_pinctrl_omit-v1-1-5a3d40046b10@foss.st.com
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>