dts: arm: st: h7: remove HASH node from H755xx

Remove the hash node from STM32755x SoC DTSI. The node was broken
(wrong node name and compatible property) and seems unused and moreover
most STM32H7xx have an HASH peripheral so a proper fix would rather
be to add the node to all relevant SoC. This will be done later, if
the need arises and after proper validation.

Signed-off-by: Etienne Carriere <etienne.carriere@st.com>