arm64: dts: imx95: Correct the range of PCIe app-reg region

Correct the range of PCIe app-reg region from 0x2000 to 0x4000 refer to
SerDes_SS memory map of i.MX95 Rerference Manual.

Fixes: 3b1d5deb ("arm64: dts: imx95: add pcie[0,1] and pcie-ep[0,1] support")
Signed-off-by: Richard Zhu <hongxing.zhu@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>