arm64: dts: librem5-devkit: increase the VBUS current in the kernel

The poly fuses can handle 6V 4Amps so incease the kernel limts to 5V
3.5Amps.

Signed-off-by: Angus Ainslie (Purism) <angus@akkea.ca>
Signed-off-by: Martin Kepplinger <martin.kepplinger@puri.sm>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>