xtensa: drop set_except_vector declaration

There's no implementation for set_except_vector function in the xtensa
code. Drop its declaration.

Signed-off-by: Max Filippov <[e-mail]>

arch/xtensa/include/uapi/asm/setup.h

···
 
 #define COMMAND_LINE_SIZE	256
 
-extern void set_except_vector(int n, void *addr);
-
 #endif