wl1271: fix wl1271_spi driver name

When forward porting some patches to upstream, there was a mistake and the
wl1271_spi driver name remained, erroneously, as "wl1271".  This patch fixes
that.

Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>