staging: wilc1000: rename u32SendBufferSize in wilc_mq_send

This patch renames u32SendBufferSize to send_buf_size to avoid
camelcase.

Signed-off-by: Chaehyun Lim <chaehyun.lim@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>