Bluetooth: hci_bcm: Sleep instead of spinning

The driver calls mdelay(15) in the ->suspend, ->resume, ->runtime_suspend
and ->runtime_resume hook, however spinning for such a long period of
time is discouraged as per Documentation/timers/timers-howto.txt.

The use of mdelay() seems unnecessary, it is allowed to sleep in the
system sleep and runtime PM hooks (with the exception of ->suspend_noirq
and ->resume_noirq) and the driver itself also does not rely on a
non-sleeping ->runtime_resume as the only place where a synchronous
resume is performed, in bcm_dequeue(), is called from a work item in
hci_ldisc.c and hci_serdev.c.

So replace the mdelay(15) with msleep(15).

Note that the delay is inserted after asserting or deasserting the
device wake pin, but in bcm_gpio_set_power() that pin is asserted or
deasserted *without* observing a delay.  It is thus unclear if the delay
is necessary at all.  It is likewise unclear why it is exactly 15 ms,
the commit introducing it, 118612fb ("Bluetooth: hci_bcm: Add
suspend/resume PM functions"), does not provide a rationale.

Cc: Frédéric Danis <frederic.danis.oss@gmail.com>
Suggested-and-reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>