gallium/inlines: remove atomic set from pipe_reference_init()

when an object is initialized with this, it should not be visible to any
other threads or contexts, so there should be no need to use an atomic set here

at the time of this commit, there are only two callers in the tree which pass
values != 1:
* zink uses a calculated number for framebuffer refcount on init (this is fine)
* aux/pb passes 0 on init (this is fine)

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10650>

src/gallium/auxiliary/util/u_inlines.h

@@ -55,7 +55,7 @@ extern "C" {
 static inline void
 pipe_reference_init(struct pipe_reference *dst, unsigned count)
 {
-   p_atomic_set(&dst->count, count);
+   dst->count = count;
 }
 
 static inline boolean