MIPS: Clarify the comment for `__cpu_has_fpu'

Reword the comment for `__cpu_has_fpu' to make it unambiguous this code
is for external floating-point units only, generally MIPS I processors
using the original CP1 hardware interface.
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9673/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/cpu-probe.c

@@ -193,7 +193,7 @@ static inline unsigned long cpu_get_fpu_id(void)
 }
 
 /*
- * Check the CPU has an FPU the official way.
+ * Check if the CPU has an external FPU.
  */
 static inline int __cpu_has_fpu(void)
 {