sound: oss: Remove useless initialisation

Remove useless initialisation of variable whose value is reinitialised
later.

The Coccinelle semantic patch used to make this change is as follows:
@@
type T;
identifier x;
constant C;
expression e;
@@

T x
- = C
 ;
x = e;

Signed-off-by: Amitoj Kaur Chawla <amitoj1606@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>