MAINTAINERS: update "ARM/OXNAS platform support" patterns

Commit 9e6c62b0 ("ARM: dts: rename oxnas dts files") renamed the
files, update the patterns.

[akpm@linux-foundation.org: crunch into a single globbed term, per Arnd]
Link: http://lkml.kernel.org/r/b39d779e143b3c0a4e7dff827346e509447e3e8e.1517147485.git.joe@perches.com


Signed-off-by: Joe Perches <joe@perches.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Daniel Golle <daniel@makrotopia.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>