Trying to do unaligned access of coherent memory on AArch64 will lead
to an abort and some parts of our IP stack will do exactly that with
received packet buffer by using memcpy() to extracts parts of it.

Convert the driver to use regular memory for received data buffers to
prevent the issue from happening.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>