sp: align stack pointer

According to ARM ARM, stack pointer has to be 16 byte aligned. Since
__stack_end is where the stack pointer is initialized, it has to be
16 byte aligned.

Signed-off-by: Davidson K <davidson.kumaresan@arm.com>
Change-Id: Ie93bf91459c96f4147c36f22f2d9b758057cd80e
diff --git a/environments/sp/sp.ld.S b/environments/sp/sp.ld.S
index 7a57a97..ac29bb1 100644
--- a/environments/sp/sp.ld.S
+++ b/environments/sp/sp.ld.S
@@ -97,10 +97,10 @@
 		__bss_end = .;
 	}
 	.stack : {
-		. = ALIGN(4);
+		. = ALIGN(16);
 		__stack_start = .;
 		. += SP_STACK_SIZE;
-		. = ALIGN(4);
+		. = ALIGN(16);
 		__stack_end = .;
 	}