SUNRPC: Return true/false (not 1/0) from bool functions

Return boolean values ("true" or "false") instead of 1 or 0 from bool
functions.  This fixes the following warnings from coccicheck:

./fs/nfsd/nfs2acl.c:289:9-10: WARNING: return of 0/1 in function
'nfsaclsvc_encode_accessres' with return type bool
./fs/nfsd/nfs2acl.c:252:9-10: WARNING: return of 0/1 in function
'nfsaclsvc_encode_getaclres' with return type bool

Signed-off-by: Haowen Bai <baihaowen@meizu.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>