percpu: simplify pcpu_setup_first_chunk()

Now that all first chunk allocator helpers allocate and map the first
chunk themselves, there's no need to have optional default alloc/map
in pcpu_setup_first_chunk().  Drop @populate_pte_fn and only leave
@dyn_size optional and make all other params mandatory.

This makes it much easier to follow what pcpu_setup_first_chunk() is
doing and what actual differences tweaking each parameter results in.

[ Impact: drop unused code path ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index 9f6bfd7..ec64357 100644
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -66,9 +66,8 @@
 
 extern size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
 				size_t static_size, size_t reserved_size,
-				ssize_t dyn_size, ssize_t unit_size,
-				void *base_addr,
-				pcpu_fc_populate_pte_fn_t populate_pte_fn);
+				ssize_t dyn_size, size_t unit_size,
+				void *base_addr);
 
 extern ssize_t __init pcpu_embed_first_chunk(
 				size_t static_size, size_t reserved_size,