[GPU] accuracy issue fix with fp16 for gemm_tiled_opt kernel

[sungeunk]

Description of the issue(symptom, root-cause, how it was resolved)

• Fixed the use of float accumulators for intermediate calculations.
• Corrected the use of float inputs for MAD operations.

The code and line that caused this issue (if it is not changed directly)

• src\plugins\intel_gpu\src\kernel_selector\cl_kernels\gemm_tiled_opt.cl

Reproduction step and snapshot (if applicable. Do not attach for customer model)

• reproducer is attached in the ticket.

Checklist

• Is it a proper fix? (not a workaround)
• Did you include test case for this fix, if necessary?
• Did you review existing test that can be extended to cover this scenario? Which test did you review?

Tickets:

• 179229