arm64: dts: imx8mp: fix address length for LCDIF2

0x238 is the offset for PANIC0_THRES, so the length needs to be greater
than that. Use the size from memory map from reference manual.

Fixes: 94e6197d ("arm64: dts: imx8mp: Add LCDIF2 & LDB nodes")
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>