kselftest: alsa: fixed a print formatting warning

kselftest: alsa: fixed a print formatting warning

[ Upstream commit 13d605e32e4cfdedcecdf3d98d21710ffe887708 ]

A statement used %d print formatter where %s should have
been used. The same has been fixed in this commit.

Signed-off-by: Ghanshyam Agrawal <ghanshyam1898@gmail.com>
Link: 5aaf9efffc57 ("kselftest: alsa: Add simplistic test for ALSA mixer controls kselftest")
Link: https://lore.kernel.org/r/20231217080019.1063476-1-ghanshyam1898@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>