net: Use ARRAY_SIZE at appropriate places

Use ARRAY_SIZE instead of having similar implementation in each drivers.
The NUMELEMS defined in drivers/net/npe/include/IxOsalTypes.h is not used
at all, so this patch removes it instead of converting it to use ARRAY_SIZE.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Ben Warren <biggerbadderben@gmail.com>
Cc: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: Joe Hershberger <joe.hershberger@ni.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Cc: TsiChungLiew <Tsi-Chung.Liew@freescale.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: York Sun <yorksun@freescale.com>