drm/imx/dcss: fix compilation issue on 32bit

When compiling for 32bit platforms, the compilation fails with:

ERROR: modpost: "__aeabi_ldivmod"
[drivers/gpu/drm/imx/dcss/imx-dcss.ko] undefined!
ERROR: modpost: "__aeabi_uldivmod"
[drivers/gpu/drm/imx/dcss/imx-dcss.ko] undefined!

This patch adds a dependency on ARM64 since no 32bit SoCs have DCSS, so far.

Signed-off-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>
Reported-by: Daniel Vetter <daniel@ffwll.ch>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20200910095250.7663-1-laurentiu.palcu@oss.nxp.com