apps/nshlib/nsh.h:  Fix typo.. #undef not #undefine.
# define HAVE_DF_HUMANREADBLE 1
# define HAVE_DF_BLOCKOUTPUT 1
# if defined(CONFIG_FS_PROCFS_EXCLUDE_USAGE)
-# undefine HAVE_DF_HUMANREADBLE
+# undef HAVE_DF_HUMANREADBLE
# endif
# if defined(CONFIG_FS_PROCFS_EXCLUDE_BLOCKS)
-# undefine HAVE_DF_BLOCKOUTPUT
+# undef HAVE_DF_BLOCKOUTPUT
# endif
#endif
