PPC: epapr: create define for return code value of success

#define _EV_HCALL_TOKEN(id, num) (((id) << 16) | (num))

#define EV_HCALL_TOKEN(hcall_num) _EV_HCALL_TOKEN(EV_EPAPR_VENDOR_ID, hcall_num)

/* epapr error codes */

/* epapr return codes */

#define EV_SUCCESS		0

#define EV_EPERM		1	/* Operation not permitted */

#define EV_ENOENT		2	/*  Entry Not Found */

#define EV_EIO			3	/* I/O error occured */