MAINTAINERS: pxa: remove Compulab arm/pxa support

These boards support is removed from the kernel, so remove the
MAINTAINERS entry for them.

Link: https://lore.kernel.org/r/20200521185140.27276-2-robert.jarzmik@free.fr


Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Acked-by: Mike Rapoport <rppt@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>