arch/parisc/kernel: remove duplicate include in ptrace

'linux/compat.h' included in 'arch/parisc/kernel/ptrace.c' is duplicated.
It is also included in the 24th line.

Signed-off-by: Zhang Yunkai <zhang.yunkai@zte.com.cn>
Signed-off-by: Helge Deller <deller@gmx.de>