drm/edid: fix Baseline_ELD_Len field in drm_edid_to_eld()

The Baseline_ELD_Len field does not include ELD Header Block size.

From High Definition Audio Specification, Revision 1.0a:

	The header block is a fixed size of 4 bytes. The baseline block
	is variable size in multiple of 4 bytes, and its size is defined
	in the header block Baseline_ELD_Len field (in number of
	DWords).

Do not include the header size in Baseline_ELD_Len field. Fix all known
users of eld[2].

While at it, switch to DIV_ROUND_UP instead of open coding it.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Dave Airlie <airlied@linux.ie>
[danvet: Fix compile fail in nouveau.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>