net: wireless: bcmdhd: Combined patch from 4.218.248-31

net: wireless: bcmdhd: Combined patch from 4.218.248-31

bcmdhd: Allocate skb with GFP_KERNEL flag if possible: fix for older kernels.
bcmdhd: Fix race conditions for sysioc_thread
    * Fix up formatting and #ifdefs.
net: wireless: bcmdhd: Fix get_customized_country_code() for older kernels.
net: wireless: bcmdhd: Move PNO function prototypes to dhd.h.
Add private command support.
net: wireless: bcmdhd: Set proper read barrier
net: wireless: bcmdhd: Fix memory leak in case of dhd_bus_init() failure
net: wireless: bcmdhd: Fix wake_lock symmetry
net: wireless: bcmdhd: Ignore error if scan results are empty
net: wireless: bcmdhd: Add sdlock to firmware loading
net: wireless: bcmdhd: Fix watchdog syncronization during start/stop
net: wireless: bcmdhd: Fix Makefile to allow WEXT compilation

Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>