libceph: use (void *) for untyped data in osd ops

Two of the fields defining osd operations are defined using (char *)
while the data they represent are really untyped, not character
strings.  Change them to have type (void *).
Signed-off-by: NAlex Elder <elder@inktank.com>
Reviewed-by: NJosh Durgin <josh.durgin@inktank.com>

include/linux/ceph/osd_client.h

@@ -184,7 +184,7 @@ struct ceph_osd_req_op {
 		} extent;
 		struct {
 			const char *name;
-			const char  *val;
+			const void *val;
 			u32 name_len;
 			u32 value_len;
 			__u8 cmp_op;       /* CEPH_OSD_CMPXATTR_OP_* */
@@ -193,7 +193,7 @@ struct ceph_osd_req_op {
 		struct {
 			const char *class_name;
 			const char *method_name;
-			const char *indata;
+			const void *indata;
 			u32 indata_len;
 			__u8 class_len;
 			__u8 method_len;