arm: Rename hdmi_if.m to crtc_if.m

There is nothing hdmi related in this interface, it's just a generic interface
for crt controller so rename it.
This also remove the 'hdmi' device used in arm kernel config. 'vt' now controls
if we build this interface (sc(4) isn't supported on arm).

Sponsored by: Beckhoff Automation GmbH & Co. KG
Reviewed by: andrew
Differential Revision: https://reviews.freebsd.org/D39120