nfsclient: Fix for short enums

The XDR library has a problem on architectures with short enums like the
default ARM EABI.  Short enums means that the size of the enum type is
variable and the smallest integer type to hold all enum values will be
selected.  For many enums this is char.  The XDR library uses int32_t
for enum_t.  There are several evil casts from an enum type to enum_t
which leads to invalid memory accesses on short enum architectures.  A
workaround is to add appropriate dummy enum values.

cpukit/libfs/src/nfsclient/proto/nfs_prot.h

@@ -48,6 +48,7 @@ enum nfsstat {
 	NFSERR_DQUOT = 69,
 	NFSERR_STALE = 70,
 	NFSERR_WFLUSH = 99,
+  _NFSSTAT = 0xffffffff
 };
 typedef enum nfsstat nfsstat;
 
@@ -61,6 +62,7 @@ enum ftype {
 	NFSOCK = 6,
 	NFBAD = 7,
 	NFFIFO = 8,
+  _FTYPE = 0xffffffff
 };
 typedef enum ftype ftype;