dt-bindings: clock: st,stm32mp1-rcc: complete the reference path

dt-bindings: clock: st,stm32mp1-rcc: complete the reference path

All other paths referenced in the file follow a scheme starting from the
Linux root. The patch adjusts the single file that deviated from this
scheme, making it consistent with the others.

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Link: https://lore.kernel.org/r/20241231150144.4035938-2-dario.binacchi@amarulasolutions.com
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>