MAINTAINERS: correct typo in new NXP LAYERSCAPE GEN4

MAINTAINERS: correct typo in new NXP LAYERSCAPE GEN4

Commit 46629b2ccc6f ("dt-bindings: PCI: Add NXP Layerscape SoCs PCIe Gen4
controller") includes a new entry in MAINTAINERS, but slipped in a typo in
one of the file entries.

Hence, since then, ./scripts/get_maintainer.pl --self-test complains:

  warning: no file matches F: \
    drivers/pci/controller/mobibeil/pcie-layerscape-gen4.c

Correct the typo in PCI DRIVER FOR NXP LAYERSCAPE GEN4 CONTROLLER.

Link: https://lore.kernel.org/r/20200506052130.5780-1-lukas.bulwahn@gmail.com
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Rob Herring <robh@kernel.org>