msm: mdss: edid: modify the extended data block's length check

EDID parser is validating the minimum length of Extended data blocks
before parsing them. Current minimum length is 2 bytes but some
extended data block like Y420CMDB's length can be 1 data byte.
Modify the minimum length to 1 data byte.

Change-Id: Iecbfbfa216160a93101a8051cd1ddef5c0426e77
Signed-off-by: Narender Ankam <nankam@codeaurora.org>