net: dwc: Fix cache alignment issues

Fix remaining cache alignment issues in the DWC Ethernet driver.
Please note that the cache handling in the driver is making the
code hideous and thus the next patch cleans that up. In order to
make this change reviewable though, the cleanup is split from it.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <clsee@altera.com>
Cc: Dinh Nguyen <dinguyen@altera.com>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Tom Rini <trini@ti.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Pavel Machek <pavel@denx.de>
Cc: Joe Hershberger <joe.hershberger@gmail.com>
Acked-by: Pavel Machek <pavel@denx.de>