percpu: indent the population block in pcpu_alloc()

percpu: indent the population block in pcpu_alloc()

The next patch will conditionalize the population block in
pcpu_alloc() which will end up making a rather large indentation
change obfuscating the actual logic change.  This patch puts the block
under "if (true)" so that the next patch can avoid indentation
changes.  The defintions of the local variables which are used only in
the block are moved into the block.

This patch is purely cosmetic.

Signed-off-by: Tejun Heo <tj@kernel.org>