habanalabs/uapi: move uapi file to drm

Move the habanalabs.h uapi file from include/uapi/misc to
include/uapi/drm, and rename it to habanalabs_accel.h.

This is required before moving the actual driver to the accel
subsystem.

Update MAINTAINERS file accordingly.

Signed-off-by: Oded Gabbay <ogabbay@kernel.org>