linker: Remove unused (OPTIONAL) from linker scripts

(OPTIONAL) was a vestiage from the initial import of the Zephyr code
base and we dont utilize it with the GNU linker.  Additionally, the way
(OPTIONAL) gets defined to nothing creates a linker script that lld
(from llvm) doesn't like.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>
diff --git a/scripts/gen_app_partitions.py b/scripts/gen_app_partitions.py
index dcdab84..0cc95ba 100644
--- a/scripts/gen_app_partitions.py
+++ b/scripts/gen_app_partitions.py
@@ -79,7 +79,7 @@
 """
 
 linker_start_seq = """
-	SECTION_PROLOGUE(_APP_SMEM_SECTION_NAME, (OPTIONAL),)
+	SECTION_PROLOGUE(_APP_SMEM_SECTION_NAME,,)
 	{
 		APP_SHARED_ALIGN;
 		_app_smem_start = .;