drivers: clock_control: stm32: enable clocks for SRAM1 and SRAM2

enables the AHB2 peripheral clocks for SRAM1 and SRAM2
on STM32H7RSX series using LL_AHB2_GRP1_EnableClock.

These clocks are required to access the corresponding SRAM regions
during runtime.

Fixes potential access faults when using SRAM1 and SRAM2.

Signed-off-by: Fabrice DJIATSA <fabrice.djiatsa-ext@st.com>