b43: fix two warnings

My gcc appears to be able to see past the function
boundary and notices that the variable 'behaviour'
could be used uninitialised:

drivers/net/wireless/b43/leds.c: In function ‘b43_leds_register’:
drivers/net/wireless/b43/leds.c:339: warning: ‘behaviour’ may be used uninitialized in this function
drivers/net/wireless/b43/leds.c: In function ‘b43_leds_init’:
drivers/net/wireless/b43/leds.c:262: warning: ‘behaviour’ may be used uninitialized in this function

because b43_led_get_sprominfo() didn't initialise
it in all cases.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>