soc: stm32g0: pm_power_ functions should be __weak
soc: stm32g0: pm_power_ functions should be __weak

In commit "pm: Fix weak linkage symbols" (PR #35274),
PM SoC hooks were converted to __weak to avoid clash with
new definition of these symbols in subsys/pm/power.c.

G0 power implementation was implemented in parallel
with this change and missed the update.

Signed-off-by: Erwan Gouriou <de4d967452b83bb0e37525652734e7d9163b6a4c@linaro.org>

galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr