arm64: dts: imx95-19x19-evk: Fix PCIe EP vpcie-supply

arm64: dts: imx95-19x19-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 imx95-19x19-evk:
- reg_pcie0 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: 58bea81052d0 ("arm64: dts: imx95: add pcie1 ep overlay file and create pcie-ep dtb files")
Signed-off-by: Sherry Sun <sherry.sun@nxp.com>
Reviewed-by: Richard Zhu <hongxing.zhu@nxp.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>