The current code is using the maximum of the source line size and the
destination line size to compute the size of the LBM to allocate.

While this is simpler, it starts to be an issue with modes such as 4k with
a quite long that will consume all the available memory, so we no longer
have that luxury.
Signed-off-by: NDave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: NMaxime Ripard <maxime@cerno.tech>
Tested-by: NChanwoo Choi <cw00.choi@samsung.com>
Tested-by: NHoegeun Kwon <hoegeun.kwon@samsung.com>
Tested-by: NStefan Wahren <stefan.wahren@i2se.com>
Link: https://patchwork.freedesktop.org/patch/msgid/b9e091883a4f7395c5b6a4f7c6070225934293db.1599120059.git-series.maxime@cerno.tech