USB: fix Queue Element Transfer Descriptor changes

USB: fix Queue Element Transfer Descriptor changes

Commit 3ed1607 "USB: sync Queue Element Transfer Descriptor against
EHCI spec" added an "__attribute__ ((aligned (32)))" to the
declaration of struct qTD, as used for example in the Linux kernel as
well.

However, it turns out that this attribute causes errors in "usb start"
(like "ERROR: NOT USB_CONFIG_DESC 7b" and similar). Drop the attribute
again.

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Dan Lykowski <lykowdk@gmail.com>
Cc: Remy Bohmer <linux@bohmer.net>
Cc: Stefano Babic <sbabic@denx.de>