arecord: Remove only regular files

arecord: Remove only regular files

arecord removes a file before writing into it. It's not
appropriate in some cases. For example, if you a pass
a symlink to a file, then the symlink will be removed
while the user expects to record into the symlink's target.
Another case is recording into the device file. Some
modems provide a tty device file as a voice device.
And it's not possible to write into it under root with
arecord, because it removes the device file.

So check the type of a file before writing into it and
remove only regular files.

Signed-off-by: Alexander Volkov <a.volkov@rusbitech.ru>
Signed-off-by: Takashi Iwai <tiwai@suse.de>