e2fsprogs: fix missing fallocate64() on nios2

e2fsprogs: fix missing fallocate64() on nios2

(external) nios2 toolchain is currently missing the fallocate64 system
call. Because of compiling the e2fsprogs package with _FILE_OFFSET_BITS=64,
_LARGEFILE_SOURCE and _LARGEFILE64_SOURCE the fallocate call is replaced
by fallocate64 by the glibc. Therefore fallocate is entirely disabled while
configuring the package.

Fixes http://autobuild.buildroot.org/results/70a/70a47bd7392560cbc1c64769c8357c0b4c91ca3b/

Signed-off-by: Frank Bergmann <frank@frajasalo.de>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>