x86: kernel/check.c simple_strtoul cleanup

Change set_corruption_check() and set_corruption_check_period()
in kernel/check.c to call kstrtoul() instead of calling
obsoleted simple_strtoul().

Signed-off-by: Shuah Khan <shuahkhan@gmail.com>
Link: http://lkml.kernel.org/r/1336326908.2897.12.camel@lorien2


Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>