[SYCL] Remove stale code previously used for FPGA loop counts, fusion, and coalescence (#22556)
Support for the `[[intel::loop_count(N)]]`,
`[[intel::loop_count_avg(N)]]`, `[[intel::loop_count_min(N)]]`,
`[[intel::loop_count_max(N)]]`, `[[intel::loop_coalesce]]`, and
`[[intel::nofusion]]` attributes was previously removed by the following
commits.
- 7102583: [SYCL] PR 2 - Remove FPGA attributes from SYCL FE (#21722)
- 3ee6128: [SYCL] PR 6 - Remove FPGA Attributes from SYCL FE (#21785)
- 136b1cd: [SYCL] PR 1 - Remove FPGA attributes from SYCL FE (#21710)
Removal of the attributes left a few data members and related setter
functions unused. This change removes them.