fs/proc/inode.c: remove cast from memory allocation

Coccinelle emits this warning:

  WARNING: casting value returned by memory allocation function to (struct proc_inode *) is useless.

Remove unnecessary cast.

Link: http://lkml.kernel.org/r/1487745720-16967-1-git-send-email-me@tobin.ccSigned-off-by: Tobin C. Harding <me@tobin.cc>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/proc/inode.c

@@ -58,7 +58,7 @@ static struct inode *proc_alloc_inode(struct super_block *sb)
 	struct proc_inode *ei;
 	struct inode *inode;
 
-	ei = (struct proc_inode *)kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
+	ei = kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
 	if (!ei)
 		return NULL;
 	ei->pid = NULL;