tile: revert change from <asm/atomic.h> to <linux/atomic.h> in asm files

The 32-bit TILEPro support uses some #defines in <asm/atomic_32.h>
for atomic support routines in assembly.  To make this more explicit,
I've turned those includes into includes of <asm/atomic_32.h>, which
should hopefully make it clear that they shouldn't be bombed into
<linux/atomic.h> in any cleanups.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>