x86/platform: Remove unused function from apb_timer.c

x86/platform: Remove unused function from apb_timer.c

Remove the function is_apbt_capable() that is not used anywhere.

This was partially found by using a static code analysis program
called 'cppcheck'.

Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Reviewed-by: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/1419166698-2470-1-git-send-email-rickard_strandqvist@spectrumdigital.se
Signed-off-by: Ingo Molnar <mingo@kernel.org>