staging: bcm2835-audio: Drop debug messages in bcm2835-pcm.c

These debug messages worsen the code readability a lot while they give
little debuggability (which we already have via tracing, in anyway).

Let's clean them up.  This allows us to reduce the
snd_bcm2835_pcm_lib_ioctl() function to be a direct call of the
snd_pcm_lib_ioctl callback (like most other drivers do), too.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>