pod: remove the ALIGNED from the pod struct

We don't really want to do this here otherwise structs that include a
pod will be padded so that an array of those structs will be aligned.

This makes a test case fail where we have a struct with a choice_body
followed by 3 uint32_t enum values. The size with and without the
aligned attribute is different.

spa/include/spa/pod/pod.h

@@ -33,7 +33,7 @@ extern "C" {
 struct spa_pod {
 	uint32_t size;		/* size of the body */
 	uint32_t type;		/* a basic id of enum spa_type */
-} SPA_ALIGNED(SPA_POD_ALIGN);
+};
 
 #define SPA_POD_VALUE(type,pod)			(((type*)(pod))->value)