MIPS: Fix KGDB build error

<asm/ptrace.h> is exported to userland so can't include <linux/ptrace.h>,
so replace the C99 types with their basic C type equivalents.

Bug originally reported and initial patch by Yoichi Yuasa
<yoichi_yuasa@tripeaks.co.jp>.

Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>