percpu: only allow sized arch overrides for {raw|this}_cpu_*() ops

Currently, percpu allows two separate methods for overriding
{raw|this}_cpu_*() ops - for a given operation, an arch can provide
whole replacement or sized sub operations to override specific parts
of it.  e.g. arch either can provide this_cpu_add() or
this_cpu_add_4() to override only the 4 byte operation.

While quite flexible on a glance, the dual-overriding scheme
complicates the code path for no actual gain.  It compilcates the
already complex operation definitions and if an arch wants to override
all sizes, it can easily provide all variants anyway.  In fact, no
arch is actually making use of whole operation override.

Another oddity is that __this_cpu_*() operations are defined in the
same way as raw_cpu_*() but ignores full overrides of the raw_cpu_*()
and doesn't allow full operation override, so if an arch provides
whole overrides for raw_cpu_*() operations __this_cpu_*() ends up
using the generic implementations.

More importantly, it takes away the layering between arch-specific and
generic parts making it impossible for the generic part to implement
arch-independent features on top of arch-specific overrides.

This patch removes the support for whole operation overrides.  As no
arch is using it, this doesn't cause any actual difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Christoph Lameter <cl@linux.com>