btrfs: remove constant parameter to memset_extent_buffer and rename it

The only memset we do is to 0, so sink the parameter to the function and
simplify all calls. Rename the function to reflect the behaviour.

Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index bf719e3..9f8a1a3 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3743,7 +3743,7 @@
 	if (btrfs_header_level(eb) > 0) {
 		end = btrfs_node_key_ptr_offset(nritems);
 
-		memset_extent_buffer(eb, 0, end, eb->len - end);
+		memzero_extent_buffer(eb, end, eb->len - end);
 	} else {
 		/*
 		 * leaf:
@@ -3752,7 +3752,7 @@
 		start = btrfs_item_nr_offset(nritems);
 		end = btrfs_leaf_data(eb) +
 		      leaf_data_end(fs_info->tree_root, eb);
-		memset_extent_buffer(eb, 0, start, end - start);
+		memzero_extent_buffer(eb, start, end - start);
 	}
 
 	for (i = 0; i < num_pages; i++) {
@@ -5517,8 +5517,8 @@
 	}
 }
 
-void memset_extent_buffer(struct extent_buffer *eb, char c,
-			  unsigned long start, unsigned long len)
+void memzero_extent_buffer(struct extent_buffer *eb, unsigned long start,
+		unsigned long len)
 {
 	size_t cur;
 	size_t offset;
@@ -5538,7 +5538,7 @@
 
 		cur = min(len, PAGE_SIZE - offset);
 		kaddr = page_address(page);
-		memset(kaddr + offset, c, cur);
+		memset(kaddr + offset, 0, cur);
 
 		len -= cur;
 		offset = 0;