Fix following warning:
WARNING: arch/i386/kernel/built-in.o(.init.text+0x3818): Section mismatch: reference to .exit.text:cache_remove_dev (between 'cacheinfo_cpu_callback' and 'cache_sysfs_init')

It points out that a function marked __cpuexit is calling a function marked
__cpuinit => oops.

The call happens only in an error-condition which may explain why we have
not seen it before.

The offending function was not used anywhere else - so marked it __cpuexit.

Note: This warning triggers only with a local copy of modpost
      but that version will soon be pushed out.
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>