edid: Add I2C command for printing the EDID

Add a single command to read the EDID information over I2C.

For example:

SMDK5250 # i2c dev 7
Setting bus to 7
SMDK5250 # i2c edid 50
EDID version: 1.4
Product ID code: 305c
Manufacturer: AUO
Serial number: 00000000
Manufactured in week: 0 year: 2011
Video input definition: digital signal, voltage level 0, blank to black
Monitor is non-RGB
Maximum visible display size: 26 cm x 14 cm
Power management features: no active off, no suspend, no standby
Estabilished timings:
Standard timings:
        1366x768        60 Hz (detailed)
        1366x768        60 Hz (detailed)
Monitor ID: 2VD2K.B116XW

Signed-off-by: Tom Wai-Hong Tam <waihong@chromium.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>