dts: arm: st: u0: fix lpuart1/2 interrupts

Interrupt vectors for lpuart1 and lpuart2 are swapped according to the
reference manual RM0503 table 54.
Fixes the usage of the interrupt-driven uart API.

Signed-off-by: Axel Utech <utech@sofiha.de>
(cherry picked from commit 4664f600)