UBUNTU: SAUCE: shiftfs -- Fix build errors from missing fiemap definitions

UBUNTU: SAUCE: shiftfs -- Fix build errors from missing fiemap definitions

shiftfs FTBFS with 5.8-rc1:

 /tmp/kernel-sforshee-6727637082e4-45IQ/build/fs/shiftfs.c: In function 'shiftfs_fiemap':
 /tmp/kernel-sforshee-6727637082e4-45IQ/build/fs/shiftfs.c:731:13: error: dereferencing pointer to incomplete type 'struct fiemap_extent_info'
 /tmp/kernel-sforshee-6727637082e4-45IQ/build/fs/shiftfs.c:731:26: error: 'FIEMAP_FLAG_SYNC' undeclared (first use in this function); did you mean 'FS_XFLAG_SYNC'?

It seems that shiftfs was getting linux/fiemap.h included
indirectly before. Include it directly.

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>