staging: rtl8188eu: ARRAY_SIZE instead of sizeof/sizeof used

This patch inserts ARRAY_SIZE instead of sizeof(type array[])/sizeof(type),
made arraylen variable constant
and removes unnecessary default value in variable definition.

Signed-off-by: Ivan Safonov <insafonov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>