arm64: dts: imx8mp: Set SPI NOR to max 40 MHz on Data Modul i.MX8M Plus eDM SBC

arm64: dts: imx8mp: Set SPI NOR to max 40 MHz on Data Modul i.MX8M Plus eDM SBC

[ Upstream commit 13ab6f174a6b577bd7d09124b47ec8ace2682e42 ]

The SPI NOR bus routing on this board cannot go above 50 MHz,
set the clock frequency to maximum of 40 MHz to be within a
safe margin. Remove the comment as well.

Fixes: 562d222f23f0 ("arm64: dts: imx8mp: Add support for Data Modul i.MX8M Plus eDM SBC")
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>