USB: Remove unnecessary casts of void ptr returning alloc function return values

Hi,

The [vk][cmz]alloc(_node) family of functions return void pointers which
it's completely unnecessary/pointless to cast to other pointer types since
that happens implicitly.

This patch removes such casts from drivers/usb/
Signed-off-by: NJesper Juhl <jj@chaosbits.net>

drivers/usb/host/ehci-dbg.c

@@ -879,7 +879,7 @@ static int fill_buffer(struct debug_buffer *buf)
 	int ret = 0;
 
 	if (!buf->output_buf)
-		buf->output_buf = (char *)vmalloc(buf->alloc_size);
+		buf->output_buf = vmalloc(buf->alloc_size);
 
 	if (!buf->output_buf) {
 		ret = -ENOMEM;