sched: remove ARCH specific fpu_counter from task_struct

fpu_counter in task_struct was used only by sh/x86.  Both of these now
carry it in ARCH specific thread_struct, hence this can now be removed
from generic task_struct, shrinking it slightly for other arches.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul Mundt <paul.mundt@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>