xfree86: Add a xf86MonitorFindHDMIBlock()

The HDMI CEA vendor specific block has some interesting information,
such as the maximum TMDS dot clock.

v2: Don't parse CEA blocks with invalid offsets, remove spurious
    brackets (Chris Wilson)

v3: Fix the looping through the CEA data blocks, it had a typo using the
    wrong variable coming from the code it was ported from.
    Replace x << 16 + y << 8 + z by x << 16 | y << 8 | z
    (Chris Wilson)

v4: Remove the stray ';' at the end of "if (*end == 0)".
    (Dominik Behr on IRC)

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
xfree86: Refactor xf86MonitorIsHDMI() using xf86MonitorFindHDMIBlock()

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
xfree86: Use the TMDS maximum frequency to prune modes

Instead of only relying on the Range section, we can do better on
HDMI to find out what is the max dot clock the monitor supports. The
HDMI CEA vendor block adds a TMDS max freq we can use.

This makes X not prune 4k resolutions on HDMI.

v2: Replace X_INFO by X_PROBED in the message that prints the max
    TMDS frequency (Chris Wilson)

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>