alpha/boot/misc: trim unused declarations

gzip_mark() and gzip_release() are gone; there used to be two
forward declarations of each and the patch removing those suckers
had left one of each behind...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/alpha/boot/misc.c

@@ -89,8 +89,6 @@ static ulg output_ptr;
 static ulg bytes_out;
 
 static void error(char *m);
-static void gzip_mark(void **);
-static void gzip_release(void **);
 
 extern int end;
 static ulg free_mem_ptr;