Fix dynamic resampling for non-NEON devices

The stride by 16 code template automatically falls back to stride by 2
(as the NEON code template override does not occur).
As such the stride by 2 (in the switch) was removed as it was unnecessary.
Removing the if() causes the fall back to happen properly for non-NEON
compilation.

Change-Id: Ia7aec6ae1d88eb54377e56e2fb57f2ae5b74cf1b
Signed-off-by: Andy Hung <hunga@google.com>