[capi] fix some api issues for tizen release

[capi] fix some api issues for tizen release

I've checked some api issues using tizen-native-api-review-script.

So, I correct most issues but there are still remain some errors
in the "nntrainer_internal.h" file.

There are three type issues remaining yet.
- enum names should end with '_e'
- struct names should end with '_s'

But I think It would be better to do not rename these enum and
struct because it is already released in earlier version.

And, The last type issues seem to be "false positive".
I think tizen-api-review-script don't aware the macro function, etc.

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

Signed-off-by: Seungbaek Hong <sb92.hong@samsung.com>