fstrim: Use a local definition of the IOCTL FIDTRIM number

As it is not upstream, it doesn't belong in the external/kernel-headers
... or in bionic's cleaned up copy.

It matches what is in common/android-3.10.

Bug: 15593563
Change-Id: I6fa22cd823a88805ec57f973813ac69291069c7d
1 file changed