sparc64: fix build breakage introduced by percpu-convert-most patchset

Commit e74e396204bfcb67570ba4517b08f5918e69afea incorrectly added
HAVE_LEGACY_PER_CPU_AREA to sparc64 although it already has been
converted to dynamic percpu allocator.  Drop both
HAVE_{LEGACY|DYNAMIC}_PER_CPU_AREA.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: David Miller <davem@davemloft.net>