wlcore: fix some sparse warnings due to missing static declaration

There were three sparse warnings in main.c due to missing static
declaration:

  CHECK   drivers/net/wireless/ti/wlcore/main.c
drivers/net/wireless/ti/wlcore/main.c:1265:5: warning: symbol 'wl1271_validate_wowlan_pattern' was not declared. Should it be static?
drivers/net/wireless/ti/wlcore/main.c:1408:5: warning: symbol 'wl1271_convert_wowlan_pattern_to_rx_filter' was not declared. Should it be static?
drivers/net/wireless/ti/wlcore/main.c:4823:6: warning: symbol 'wl1271_connection_loss_work' was not declared. Should it be static?

Fix these by adding the static declaration to those functions.

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