arm: dts: imx93: add a per clock for LPUART1

When CLK is enabled, get_lpuart_clk_rate() needs to get a per clock of
lpuart, so that add a per clock for lpuart1.

Signed-off-by: Alice Guo <alice.guo@nxp.com>
Reviewed-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Sébastien Szymanski <sebastien.szymanski@armadeus.com>