ALSA: mixer_oss: Remove deprecated strcpy() function calls

Remove the deprecated strcpy() function calls and assign the strings
directly to a 'char *' instead.

Use 'if/else if' instead of two separate if statements.

No functional changes intended.

Link: https://github.com/KSPP/linux/issues/88


Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Link: https://patch.msgid.link/20250623113855.37031-2-thorsten.blum@linux.dev


Signed-off-by: Takashi Iwai <tiwai@suse.de>