configure: Drop default CONFIG_LITTLE_ENDIAN for Cygwin

configure: Drop default CONFIG_LITTLE_ENDIAN for Cygwin

It's a bit strange that Cygwin is assumed to be le by default when
no other platforms have such assumption even if they only target
a single or certain arch (e.g. non-Android Linux often runs on x86,
DragonFlyBSD only runs on x86, and so on..).

Endianness will be detected by pointer arithmetic anyway, and it's
better to rely on it to handle any sort of newly supported archs
in the future.

Signed-off-by: Tomohiro Kusumi <tkusumi@tuxera.com>
Signed-off-by: Jens Axboe <axboe@fb.com>