mmc: rpmb: fix tautological condition in RPMB_REQ_READ_DATA validation

mmc: rpmb: fix tautological condition in RPMB_REQ_READ_DATA validation

In rpmb_route_frames(), the RPMB_REQ_READ_DATA case checks
"req_cnt != 1 || !req_cnt" which is tautological -- !req_cnt (req_cnt
== 0) is always a subset of req_cnt != 1. The second operand is dead
code.

Based on the pattern of all other cases in the switch (RPMB_REQ_KEY,
RPMB_REQ_WRITE_DATA, RPMB_REQ_WCOUNTER) which validate rsp_cnt, this
was meant to be "req_cnt != 1 || !rsp_cnt". Without this fix, a caller
could pass rsp_cnt=0 for a read request without validation.

Signed-off-by: Peng Fan <peng.fan@nxp.com>