ALSA: echoaudio: remove redundant assignment to variable bytes

ALSA: echoaudio: remove redundant assignment to variable bytes

The variable bytes is being assigned a value that is never read, it
is being re-assigned inside a following if block. The assignment is
redundant and can be removed.

Cleans up clang scan build warning:
sound/pci/echoaudio/midi.c:211:9: warning: Although the value stored
to 'bytes' is used in the enclosing expression, the value is never
actually read from 'bytes' [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20220302170728.1094633-1-colin.i.king@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>