s3/vfs: change fallocate mode flags from enum->uint32_t

s3/vfs: change fallocate mode flags from enum->uint32_t

The Linux fallocate syscall offers a mode parameter which can take the
following flags:
FALLOC_FL_KEEP_SIZE
FALLOC_FL_PUNCH_HOLE (since 2.6.38)
FALLOC_FL_COLLAPSE_RANGE (since 3.15)
FALLOC_FL_ZERO_RANGE (since 3.14)

The flags are not exclusive, e.g. FALLOC_FL_PUNCH_HOLE must be specified
alongside FALLOC_FL_KEEP_SIZE.

Samba currently takes a vfs_fallocate_mode enum parameter for the VFS
fallocate hook, taking either an EXTEND_SIZE or KEEP_SIZE value. This
commit changes the fallocate hook such that it accepts a uint32_t flags
parameter, in preparation for PUNCH_HOLE and ZERO_RANGE support.

Signed-off-by: David Disseldorp <ddiss@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>