refactor(st-ddr): add definition for timeouts and delays

Instead of using hard-coded number in DDR driver, use macros.
Modify TIMEOUT_US_1S to DDR_TIMEOUT_US_1S to align with other defines.

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: I489084132821774b0049a4a5d7fc30db24a7bb11
3 files changed