drm/qxl: fix qxl can't use in arm64

drm/qxl: fix qxl can't use in arm64

qxl use ioremap to map ram_header and rom, in the arm64 implementation,
the device is mapped as DEVICE_nGnRE, it can not support unaligned
access. and qxl is a virtual device, it can be treated more like RAM
than actual MMIO registers. use ioremap_wc() replace it.

Signed-off-by: Cong Liu <liucong2@kylinos.cn>
Acked-by: Christian König <christian.koenig@amd.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20220324104928.2959545-1-liucong2@kylinos.cn
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>