ARM: kprobes: Fix compilation error caused by superfluous '*'

There is a superfluous '*' in the definition of kprobe_decode_insn_t
which on older versions of GCC (4.2.4) causes the compilation error:

In file included from arch/arm/probes/kprobes/core.c:37:
arch/arm/probes/kprobes/core.h:43: error: '[*]' not allowed in other than a declaration

Fix this by removing the unneeded character.

Reported-by: Janusz Użycki <j.uzycki@elproma.com.pl>
Signed-off-by: Jon Medhurst <tixy@linaro.org>