staging: wilc1000: remove if defined codes of USE_OLD_SPI_SW

This patch removes if defined codes of USE_OLD_SPI_SW.
This macro is deleted because it is commented out.

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