refactor(st): move macros to common folder

As these definitions will be the same for STM32MP1 and STM32MP2, move
PLATFORM_MTD_MAX_PAGE_SIZE and DWL_BUFFER_SIZE macro definition to the
file: plat/st/common/include/stm32mp_common.h

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: I480669d009d15fec753298f47b136e34fa240132
3 files changed