ALSA: pcm: Add more disconnection checks at file ops

In the case of hot-disconnection of a PCM device, all file operations
except for close should be rejected.  This patch adds more sanity
checks in the file operation code paths.

Link: https://lore.kernel.org/r/20211006142214.3089-1-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>