arm64: dts: imx93: change tuning start to get a large scan range for standard tuning

For original setting, the start point is 20, after the SION setting,
ERR052021 can be workaround, but start point from 20 is too large,
especially for the LD 133MHz case.

Set the tuning start point as 1, tuning step as 2, so that, for the
40 times tuning logic, it can cover 1~81, its large and safe enough
for all different devices like eMMC/SD/SDIO.

Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>