sp_min: allow inclusion of a platform-specific linker script

Similar to bl31 allow sp_min to also include a platform-specific
linker script. This allows for example to place specific code in
other memories of the system, like resume code in sram, while the
main tf-a lives in ddr.
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Change-Id: I67642f7bfca036b5d51eb0fa092b479a647a9cc1

bl32/sp_min/sp_min.ld.S

@@ -16,6 +16,9 @@ MEMORY {
     RAM (rwx): ORIGIN = BL32_BASE, LENGTH = BL32_LIMIT - BL32_BASE
 }
 
+#ifdef PLAT_SP_MIN_EXTRA_LD_SCRIPT
+#include <plat_sp_min.ld.S>
+#endif
 
 SECTIONS
 {