tests: drivers: stm32g0 clock control with APB1_2 RCC register

Change the name of the STM32_CLOCK_BUS_APB2 RCC resgister
of the stm32g0 to STM32_CLOCK_BUS_APB1_2
in the testcase for the stm32g0 device.

Signed-off-by: Francois Ramu <francois.ramu@st.com>