MIPS: ath25: clean up non-kernel-doc comment warning

MIPS: ath25: clean up non-kernel-doc comment warning

Don't use "/**" kernel-doc notation for comments that are not in
kernel-doc format.

Eliminates one warning:

arch/mips/pci/pci-ar2315.c:6: warning: This comment starts with
  '/**', but isn't a kernel-doc comment. Refer
  Documentation/doc-guide/kernel-doc.rst
    * Both AR2315 and AR2316 chips have PCI interface unit, which supports DMA

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kernel test robot <lkp@intel.com>
Cc: Aditya Srivastava <yashsri421@gmail.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: linux-mips@vger.kernel.org
Cc: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Acked-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>