MIPS: 'make -s' should be silent

A clean mips64 build produces no output except for two lines:

  Checking missing-syscalls for N32
  Checking missing-syscalls for O32

On other architectures, there is no output at all, so let's do the
same here for the sake of build testing. The 'kecho' macro is used
to print the message on a normal build but skip it with 'make -s'.

Fixes: e48ce6b8 ("[MIPS] Simplify missing-syscalls for N32 and O32")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: Matt Redfearn <matt.redfearn@imgtec.com>
Cc: Huacai Chen <chenhc@lemote.com>
Cc: Maarten ter Huurne <maarten@treewalker.org>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/15040/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>