stm32mp1: enable PIE for BL32

In order to prepare future support of FIP, BL32 (SP_min) is compiled
as Position Independent Executable.

Change-Id: I15e7cc433fb03e1833002f4fe2eaecb6ed42eb47
Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
4 files changed