wlcore: make wlcore_cmd_send_failsafe() static

The wlcore_cmd_send_failsafe() function is only called in the cmd.c
file, where it is definde.  Make it static.

Additionally, move the EXPORT_SYMBOL macro for wl1271_cmd_send() to
the right place.

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