arch/mips: change duplicated word in NUMA help text

Fix wording in NUMA help text.

Signed-off-by: Randy Dunlap <[e-mail]>
Cc: Ralf Baechle <[e-mail]>
Cc: Paul Burton <[e-mail]>
Cc: [e-mail]
Reviewed-by: Philippe Mathieu-Daudé <[e-mail]>
Signed-off-by: Thomas Bogendoerfer <[e-mail]>

arch/mips/Kconfig

···
 	  Say Y to compile the kernel to support NUMA (Non-Uniform Memory
 	  Access).  This option improves performance on systems with more
 	  than two nodes; on two node systems it is generally better to
-	  leave it disabled; on single node systems disable this option
+	  leave it disabled; on single node systems leave this option
 	  disabled.
 
 config SYS_SUPPORTS_NUMA