ALSA: hdsp: remove redundant assignment to pointer kctl

ALSA: hdsp: remove redundant assignment to pointer kctl

Pointer kctl is being assigned a value that is not being read, buf
is being re-assigned later. The assignment is redundant and can be
removed.

Cleans up clang scan build warning:
sound/pci/rme9652/hdsp.c:3317:28: warning: Although the value stored
to 'kctl' is used in the enclosing expression, the value is never
actually read from 'kctl' [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20220508212819.59188-1-colin.i.king@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>