sys: Extend MIPS temporary work around to all mips targets.

Extened the temporary workaround for mips boards to all mips boards
until pr#6639 is merged.

sys/posix/include/fcntl.h

@@ -15,10 +15,10 @@
  * @see http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/fcntl.h.html
  */
 
-/** @todo Remove ifdef BOARD_MIPS_MALTA special case after
+/** @todo Remove ifdef __mips__ special case after
  * [#6639](https://github.com/RIOT-OS/RIOT/pull/6639) is merged */
 #ifndef DOXYGEN
-#if defined(CPU_NATIVE) || MODULE_NEWLIB || defined(BOARD_MIPS_MALTA)
+#if defined(CPU_NATIVE) || MODULE_NEWLIB || defined(__mips__)
 /* If building on native or newlib we need to use the system header instead */
 #pragma GCC system_header
 /* without the GCC pragma above #include_next will trigger a pedantic error */

sys/posix/include/sys/statvfs.h

@@ -22,9 +22,9 @@
 #define SYS_STATVFS_H_
 
 #include <sys/types.h> /* for fsblkcnt_t, fsfilcnt_t */
-/** @todo Remove ifdef BOARD_MIPS_MALTA special case after
+/** @todo Remove ifdef __mips__ special case after
  * [#6639](https://github.com/RIOT-OS/RIOT/pull/6639) is merged */
-#if MODULE_NEWLIB || defined(BOARD_MIPS_MALTA)
+#if MODULE_NEWLIB || defined(__mips__)
 /* newlib support for fsblkcnt_t was only recently added to the newlib git
  * repository, commit f3e587d30a9f65d0c6551ad14095300f6e81672e, 15 apr 2016.
  * Will be included in release 2.5.0, around new year 2016/2017.