MAINTAINERS: drop file entry in Marvell Kirkwood and Armada SOC support

Commit fcaf733c ("MAINTAINERS: Add Falcon DB") adds a new file entry
referring to non-existing files arch/arm/boot/dts/marvell/db-falcon*.
Checking with 'find . -name db-falcon*' and the files actually added with
the commit b3370479 ("arm64: dts: a7k: add COM Express boards"), which
was part of the same patch series, the files intended to refer to are
actually arch/arm64/boot/dts/marvell/db-falcon-carrier-a7k.dts and
arch/arm64/boot/dts/marvell/db-falcon-carrier.dtsi.

Note though that there is already a file entry for
arch/arm64/boot/dts/marvell/ in the ARM/Marvell Kirkwood and Armada SOC
support section. So, the added files were already covered by the
existing MAINTAINERS file and no further file entry is required at all.

Drop the unneeded file entry, essentially reverting the commit
fcaf733c ("MAINTAINERS: Add Falcon DB").

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@redhat.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>