LoongArch: Eliminate superfluous get_numa_distances_cnt()

In LoongArch, get_numa_distances_cnt() isn't in use, resulting in a
compiler warning.

Fix follow errors with clang-18 when W=1e:

arch/loongarch/kernel/acpi.c:259:28: error: unused function 'get_numa_distances_cnt' [-Werror,-Wunused-function]
  259 | static inline unsigned int get_numa_distances_cnt(struct acpi_table_slit *slit)
      |                            ^~~~~~~~~~~~~~~~~~~~~~
1 error generated.

Link: https://lore.kernel.org/all/Z7bHPVUH4lAezk0E@kernel.org/


Signed-off-by: Yuli Wang <wangyuli@uniontech.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>