wl1271: fix endianess issues

We were not handling endianess correctly.  The wl1271 chip runs on
little-endian values.  This patch makes sure that all the communication with
the wl1271 firmware is done in little-endian by using cpu_to_le* and
le*_to_cpu where appropriate.

Also, all the struct definitions for data exchanged with the firmware has
been changed to use __le16/32 types instead of u16/32.

This fixes a few sparse warnings, such as these:

drivers/net/wireless/wl12xx/wl1271_cmd.c:554:42: warning: incorrect type in assignment (different base types)
drivers/net/wireless/wl12xx/wl1271_cmd.c:555:42: warning: incorrect type in assignment (different base types)
drivers/net/wireless/wl12xx/wl1271_cmd.c:577:58: warning: incorrect type in assignment (different base types)
drivers/net/wireless/wl12xx/wl1271_cmd.c:579:58: warning: incorrect type in assignment (different base types)
drivers/net/wireless/wl12xx/wl1271_cmd.c:676:18: warning: incorrect type in assignment (different base types)
drivers/net/wireless/wl12xx/wl1271_cmd.c:787:22: warning: incorrect type in assignment (different base types)
drivers/net/wireless/wl12xx/wl1271_cmd.c:789:21: warning: incorrect type in assignment (different base types)
drivers/net/wireless/wl12xx/wl1271_tx.c:98:47: warning: incorrect type in argument 1 (different base types)
drivers/net/wireless/wl12xx/wl1271_acx.c:932:32: warning: incorrect type in assignment (different base types)
drivers/net/wireless/wl12xx/wl1271_boot.c:191:32: warning: incorrect type in argument 1 (different base types)
drivers/net/wireless/wl12xx/wl1271_boot.c:197:38: warning: incorrect type in argument 1 (different base types)
drivers/net/wireless/wl12xx/wl1271_boot.c:199:37: warning: incorrect type in argument 1 (different base types)
drivers/net/wireless/wl12xx/wl1271_init.c:255:40: warning: incorrect type in assignment (different base types)
drivers/net/wireless/wl12xx/wl1271_init.c:275:53: warning: incorrect type in assignment (different base types)

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>