MAINTAINERS: Simplify entries for Arm Vexpress platform and related drivers

MAINTAINERS: Simplify entries for Arm Vexpress platform and related drivers

Currently the entries have regexs but in absolute paths. The "N:" entries
can deal with all files and directories irrespective of the depth/path
matching the regex patterns.

Simplifies the entry by making using "N:" and dropping "F:" with absolute
paths.

Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Lorenzo Pieralisi <lpieralisi@kernel.org>
Suggested-by: Tom Rini <trini@konsulko.com>
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://lore.kernel.org/r/20230727133551.648390-1-sudeep.holla@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>