stm32mp: remove efi_add_known_memory() function definition

stm32mp: remove efi_add_known_memory() function definition

The efi_add_known_memory() function for the stm32mp platforms is adding
the EFI_CONVENTIONAL_MEMORY type. This memory is now being handled
through the LMB module -- the lmb_add_memory() adds this memory to the
memory map. Remove the definition of the now superfluous
efi_add_known_memory() function.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Reviewed-by: Simon Glass <sjg@chromium.org>