edid: rename struct member to fix two EDID_* macros

Without this change EDID_DETAILED_TIMING_VSYNC_OFFSET
and EDID_DETAILED_TIMING_VSYNC_PULSE_WIDTH macros can
not be used (compile error).
The fix is quite trivial: rename struct member to the
expected name.

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>