adi display: keep the default edid address

BugLink: http://bugs.launchpad.net/bugs/611634

The patch fixes a bug in reading the edid data, the previous code
changes the edid address to 0x50, but, the driver reads from address
0x3f.

Signed-off-by: Eric Miao <eric.miao@canonical.com>
Signed-off-by: Brad Figg <brad.figg@canonical.com>