spl: Introduce spl_board_prepare_for_optee() hook

OP-TEE requires some particular setup, which is not needed for linux
or other payloads. Add a hook for platform-specific code to perform
any OP-TEE related configuration and initialization.

A weak function is used because it is symmetrical to other
spl_board_prepare_for_*() implementations. A solution to avoid the use
of weak functions would trivially apply to all these implementations.
However, re-designing this is beyond the scope of this patch.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
diff --git a/common/spl/spl.c b/common/spl/spl.c
index 3ec16d0..d1b072d 100644
--- a/common/spl/spl.c
+++ b/common/spl/spl.c
@@ -167,6 +167,10 @@
 	/* Nothing to do! */
 }
 
+__weak void spl_board_prepare_for_optee(void *fdt)
+{
+}
+
 __weak void spl_board_prepare_for_boot(void)
 {
 	/* Nothing to do! */
@@ -763,6 +767,7 @@
 #if CONFIG_IS_ENABLED(OPTEE)
 	case IH_OS_TEE:
 		debug("Jumping to U-Boot via OP-TEE\n");
+		spl_board_prepare_for_optee(spl_image.fdt_addr);
 		spl_optee_entry(NULL, NULL, spl_image.fdt_addr,
 				(void *)spl_image.entry_point);
 		break;