staging: wilc1000: remove duplicate null check routine

This patch removes the duplicate null check routine. The same null check
routine is twice executed. Therefore the duplicated routine is not necessary.

Signed-off-by: Leo Kim <leo.kim@atmel.com>
Signed-off-by: Tony Cho <tony.cho@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>