alpha: Fix a typo on ptrace.h

 - struct has as little information as possible. * I does not have*
 + struct has as little information as possible. *It does not have*

Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-alpha@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Matt Turner <mattst88@gmail.com>