refactor(drivers/st/clk): change fdt_get_rcc_node as static

Change the fdt_get_rcc_node function to static, as it is used only in
stm32mp_clkfunc.c file; it is only a cleanup change without functional
modification.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Change-Id: Ib4ef110f6f1b16dbaa727a065e40275d3cf58a73
2 files changed