ARM: dts: stm32: remove shmem for scmi-optee on stm32mp15

ARM: dts: stm32: remove shmem for scmi-optee on stm32mp15

Since the OP-TEE commit "plat-stm32mp1: scmi_server: default use OP-TEE
shared memory", integrated in OP-TEE 3.22.0-rc1, the default configuration
for STM32MP15x SoCs changes and CFG_STM32MP1_SCMI_SHM_SYSRAM is disabled
by default and the OP-TEE SMCI server uses OP-TEE native shared memory
registered by clients.

To be compatible with this configuration and the next OP-TEE versions,
this patch removes in the STM32MP15 SCMI device tree the SHMEM used by
OP-TEE SCMI and the associated reserved memory in the last 4KByte page
of SRAM.

Fixes: ea3414e1249e ("ARM: dts: stm32: move SCMI related nodes in a dedicated file for stm32mp15")
Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>