arm64: dts: imx8mn-evk: fix the min/max voltages of the PMIC

Use the proper voltages as supported by the board instead of the ones
supported by the PMIC. The voltages were taken from both the schematic
of the 8MNANOLPD4-EVK eval board and the datasheet of the IMX8MN SoC.

Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Heiko Thiery <heiko.thiery@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>