ALSA: echoaudio: remove redundant initialization of pointer 'pipe'

The pointer 'pipe' is being initialized with a value that is never
read and it is re-assigned later, hence the initialization is redundant
and can be removed. Also remove pointer 'runtime' as it is no longer
required.

Cleans up clang warning:
sound/pci/echoaudio/echoaudio.c:740:20: warning: Value stored to 'pipe'
during its initialization is never read

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>