mips: switch to using asm-generic for seccomp.h

Switch to using the newly created asm-generic/seccomp.h for the seccomp
strict mode syscall definitions.  COMPAT definitions retain their
overrides and the remaining definitions were identical.

Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>