Simplify NN operation registration

Prior to this change, general operation registration takes an
operation's validation function as an argument, and each operation
exposed its validation function in a header file. However, operations
that have validation functions implemented have a fixed name (provided
by NN_VALIDATION_FUNCTION_NAME).

This change introduces a new registration macro
(NN_REGISTER_OPERATION_DEFAULT_VALIDATION) to use the default validation
function with the known name, and also removes the validation functions
from the operation header files.

Bug: N/A
Test: mma
Change-Id: Icc53713edd436b07fca05c37bb27bc05280345eb
114 files changed