ALSA: ad1889: Replace mdelay with usleep_range in snd_ad1889_ac97_ready
snd_ad1889_ac97_ready() is never called in atomic context.
The call chain ending up at snd_ad1889_ac97_ready() is:
[1] snd_ad1889_ac97_ready() <- snd_ad1889_ac97_xinit() <-
snd_ad1889_ac97_init() <- snd_ad1889_probe()
snd_ad1889_probe() is only set as ".probe" in struct pci_driver.
This function is not called in atomic context.
Despite never getting called from atomic context, snd_ad1889_ac97_ready()
calls mdelay for busy wait.
This is not necessary and can be replaced with usleep_range to
avoid busy waiting.
This is found by a static analysis tool named DCNS written by myself.
Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>