2.4.13-ac8 current() changes

[Keith Owens]

2.4.13-ac8 changed get_current() to use cr2 instead of esp and
introduced hard_get_current() which uses esp.  The comment on
hard_get_current() in include/asm-i386/smp.h says "for within NMI,
do_page_fault, cpu_init".  But NMI, do_page_fault and cpu_init can
execute other code, any references to current() in that other code will
use get_current() instead of hard_get_current().

How is generic code called from NMI etc. meant to know which version of
current() to use?  Usage of current() is hidden inside a lot of other
macros, this change looks like a data mismatch just waiting to bite us.