f2fs: remove redundant initialization of pointer 'p'

Pointer p is initialized with a value that is never read and is later
re-assigned a new value, hence the initialization is redundant and can
be removed.

Cleans up clang warning:
fs/f2fs/extent_cache.c:463:19: warning: Value stored to 'p' during
its initialization is never read

Signed-off-by: Colin Ian King <[e-mail]>
Reviewed-by: Chao Yu <[e-mail]>
Signed-off-by: Jaegeuk Kim <[e-mail]>

fs/f2fs/extent_cache.c

···
 				struct rb_node *insert_parent)
 {
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
-	struct rb_node **p = &et->root.rb_node;
+	struct rb_node **p;
 	struct rb_node *parent = NULL;
 	struct extent_node *en = NULL;