ARM: shmobile: mackerel: Remove from MAINTAINERS

Remove the mackerel_defconfig from the MAINTAINERS file.
Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

MAINTAINERS

@@ -1418,7 +1418,6 @@ F:	arch/arm/configs/ape6evm_defconfig
 F:	arch/arm/configs/armadillo800eva_defconfig
 F:	arch/arm/configs/bockw_defconfig
 F:	arch/arm/configs/kzm9g_defconfig
-F:	arch/arm/configs/mackerel_defconfig
 F:	arch/arm/configs/marzen_defconfig
 F:	arch/arm/configs/shmobile_defconfig
 F:	arch/arm/include/debug/renesas-scif.S