clk: stm32mp1: add support of BSEC clock

Add the support of the BSEC clock used by the STM32MP misc driver
since the commit 622c956c ("stm32mp: bsec: manage clock when present
in device tree") even if this clock is not yet defined in kernel device
tree stm32mp151.dtsi.

This patch avoids issue for basic boot when this secure clock are not
provided by secure world with SCMI.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>