[GPU] Added multiple fp16 unittests for blas kernel operations.

      Unittest_blas_kernels_cl.cpp updated with fp16 unittests.

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

Signed-off-by: Niket Agarwal <niket.a@samsung.com>

Author: niket-agarwal