arm64: dts: imx8mq-librem5-r4: Bump up proximity sensor's near level

There is at least one Evergreen phone out there that reports levels
of 5-6 at rest: https://gitlab.gnome.org/GNOME/calls/-/issues/560



Signed-off-by: Sebastian Krzyszkowiak <sebastian.krzyszkowiak@puri.sm>
Signed-off-by: Martin Kepplinger <martin.kepplinger@puri.sm>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>