wl1271: fix sparse warnings about undeclared functions

The following sparse warnings were fixed:

drivers/net/wireless/wl12xx/wl1271_spi.c:199:6: warning: symbol 'wl1271_spi_read_busy' was not declared. Should it be static?
drivers/net/wireless/wl12xx/wl1271_cmd.c:84:5: warning: symbol 'wl1271_cmd_cal_channel_tune' was not declared. Should it be static?
drivers/net/wireless/wl12xx/wl1271_cmd.c:107:5: warning: symbol 'wl1271_cmd_cal_update_ref_point' was not declared. Should it be static?
drivers/net/wireless/wl12xx/wl1271_cmd.c:132:5: warning: symbol 'wl1271_cmd_cal_p2g' was not declared. Should it be static?
drivers/net/wireless/wl12xx/wl1271_cmd.c:153:5: warning: symbol 'wl1271_cmd_cal' was not declared. Should it be static?

Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Reviewed-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>