[ALSA] Fix permissions in some /proc files

PCM Midlevel,CA0106 driver,EMU10K1/EMU10K2 driver
Fix by Guillaume Chazarain <guichaz@yahoo.fr>:

Some tunables in /proc have a write() function, but as their
permission does not reflect it, it can be confusing to the user.

So here is a patch that corrects the mode of those files. Note that I
have only tested the 'xrun_debug' entry.

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