dmaengine: bestcomm: fix system boot lockups

dmaengine: bestcomm: fix system boot lockups

memset() and memcpy() on an MMIO region like here results in a
lockup at startup on mpc5200 platform (since this first happens
during probing of the ATA and Ethernet drivers). Use memset_io()
and memcpy_toio() instead.

Fixes: 2f9ea1bde0d1 ("bestcomm: core bestcomm support for Freescale MPC5200")
Cc: stable@vger.kernel.org # v5.14+
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Link: https://lore.kernel.org/r/20211014094012.21286-1-agust@denx.de
Signed-off-by: Vinod Koul <vkoul@kernel.org>