Revert "usb: host: ehci: Use dma_pool_zalloc()"

This reverts commit 22072e83

 as it is
broken.

Alan writes:
	What you can't see just from reading the patch is that in both
	cases (ehci->itd_pool and ehci->sitd_pool) there are two
	allocation paths -- the two branches of an "if" statement -- and
	only one of the paths calls dma_pool_[z]alloc.  However, the
	memset is needed for both paths, and so it can't be eliminated.
	Given that it must be present, there's no advantage to calling
	dma_pool_zalloc rather than dma_pool_alloc.

Reported-by: Erick Cafferata <erick@cafferata.me>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>