MAINTAINERS: adjust to renaming physmap_of_versatile.c

MAINTAINERS: adjust to renaming physmap_of_versatile.c

Commit 6ca15cfa0788 ("mtd: maps: Rename physmap_of_{versatile, gemini}
into physmap-{versatile, gemini}") renamed physmap_of_versatile.c to
physmap-versatile.c, but did not adjust the MAINTAINERS entry.

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

  warning: no file matches F: drivers/mtd/maps/physmap_of_versatile.c

Rectify the ARM INTEGRATOR, VERSATILE AND REALVIEW SUPPORT entry and now
also cover drivers/mtd/maps/physmap-versatile.h while at it.

Co-developed-by: Sebastian Duda <sebastian.duda@fau.de>
Signed-off-by: Sebastian Duda <sebastian.duda@fau.de>
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20200418100933.8012-1-lukas.bulwahn@gmail.com
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>