MAINTAINERS: rectify entry for ARM/HPE GXP ARCHITECTURE

Commit 8cc35b86 ("spi: dt-bindings: add documentation for
hpe,gxp-spifi") adds the spi dt-binding file hpe,gxp-spifi.yaml and commit
a1848b0f

 ("MAINTAINERS: add spi support to GXP") adds a file entry
hpe,gxp-spi.yaml in ARM/HPE GXP ARCHITECTURE. Note the different file name.

Hence, ./scripts/get_maintainer.pl --self-test=patterns complains about a
broken reference.

Repair this file reference in ARM/HPE GXP ARCHITECTURE.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20220804161823.20912-1-lukas.bulwahn@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>