When copying partial framebuffer regions line by line, there is overhead
from multiple memcpy() calls.
Optimise video_flush_copy() to detect when entire lines are being copied
(damage spans full width) and perform a single memcpy() for the whole
region instead of looping line by line.
Also invert the early-exit check to reduce nesting.
Co-developed-by: Claude <noreply@anthropic.com>
Signed-off-by: Simon Glass <simon.glass@canonical.com>
e68bb75109