kmod: fix varargs kernel-doc

Fix varargs kernel-doc format in kmod.c:
Use @... instead of @varargs.

Warning(kernel/kmod.c:67): Excess function parameter or struct member 'varargs' description in 'request_module'

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>