[MIPS] Fix warning about unused definition in c-sb1.c

arch/mips/mm/c-sb1.c: In function `sb1_cache_init':
arch/mips/mm/c-sb1.c:447: warning: unused variable `handle_vec2_sb1'

Signed-off-by: Yoichi Yuasa <[e-mail]>
Signed-off-by: Ralf Baechle <[e-mail]>

arch/mips/mm/c-sb1.c

···
 void sb1_cache_init(void)
 {
 	extern char except_vec2_sb1;
-	extern char handle_vec2_sb1;
 
 	/* Special cache error handler for SB1 */
 	set_uncached_handler (0x100, &except_vec2_sb1, 0x80);