net: usb: r8152: Use ALLOC_CACHE_ALIGN_BUFFER() to allocate the buffers

Testing on theadorable (Armada XP) has shown, that using this driver
results in many cache misaligned warning, such as:

CACHE: Misaligned operation at range [7fabd8fc, 7fabd900]

This patch now uses the ALLOC_CACHE_ALIGN_BUFFER() macro to allocate the
buffers on a cache aligned boundary. This fixes all warnings seen on the
Armada XP platform.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Ted Chen <tedchen@realtek.com>
Cc: Joe Hershberger <joe.hershberger@ni.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>