arm64: dts: imx943-evk: Fix PCIe EP vpcie-supply

arm64: dts: imx943-evk: Fix PCIe EP vpcie-supply

The vpcie-supply property should reference the regulator that controls
the actual M.2 power supply, not the W_DISABLE1# signal.
On imx943-evk:
- reg_m2_wlan controls M.2 W_DISABLE1# signal
- reg_m2_pwr controls the actual M.2 power supply

Fix the vpcie-supply to use reg_m2_pwr for proper power control in
PCIe endpoint mode.

Fixes: 1962c596d51c ("arm64: dts: imx943-evk: Add pcie[0,1] and pcie-ep[0,1] support")
Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>