edid: remove float use

First, we don't want floats in our code base.
Second, the calculation of the aspect ratio was wacky,
using a value guaranteed to be 0 for aspect ratio calculation.

While at it, define the aspect_* fields to be in tenths, to
provide some additional resolution. They were like that already
but we now also commit to that.

Change-Id: I5511adf4bf76cdd6a69240491372f220ef1aa687
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: http://review.coreboot.org/7803
Reviewed-by: Marc Jones <marc.jones@se-eng.com>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Tested-by: build bot (Jenkins)