net/hookers: only enable on x86 platform

read/write_cr0() are used in net/hookers.c, but they are only available
on x86 platform. Adding a depend-on fields in Kconfig to disable this
feature in other platforms.
Reported-by: Nkbuild test robot <lkp@intel.com>
Signed-off-by: NCaspar Zhang <caspar@linux.alibaba.com>
Reviewed-by: NJoseph Qi <joseph.qi@linux.alibaba.com>

net/hookers/Kconfig

 config HOOKERS
        tristate "Hooker service"
        default m
+       depends on X86
        ---help---
        Allow replacing and restore the function pointer in any order.
        See include/linux/hookers.h for details.
 
-       Say m if unsure.
\ No newline at end of file
+       Say m if unsure.