wl1251: change wake_up_conditions config

wl1251: change wake_up_conditions config

Setting BEACON_BITMAP (or never sending wake_up_conditions at all) reduces
ping times from external device from jumping between to 20-230ms to 20-100ms
and gives better ssh experience.
The power usage increase was measured to be ~8mA@4.1V, so I consider it
worth it (in comparison, connected and idle USB wifi dongle draws ~150mA
from the battery).

There is a new sysfs file to enable old behavior:
/sys/bus/mmc/devices/mmc2\:0001/mmc2\:0001\:1/long_doze_mode
but the command is only sent once.

Hopefully this will improve router compatibility too.
note: WAKE_UP_EVENT_DTIM_BITMAP is called "long doze mode" by TI driver.