[layers/activation_func] Apply template on activation functions

[layers/activation_func] Apply template on activation functions

**Changes proposed in this PR:**

- For mixed precision, activation functions should be revised to a function template to avoid bulky code
- In order to use function template for setActivation, we need another function template to handle multiple types of activation function
- Minor fixes for template instantiation, and this will be revised proplerly for fp16 use in the next PR

Resolves:

**Self evaluation:**
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2. Run test:     [X]Passed [ ]Failed [ ]Skipped

Signed-off-by: skykongkong8 <ss.kong@samsung.com>