mei: pxp: fix mei_pxp_send_message return value

mei: pxp: fix mei_pxp_send_message return value

mei_pxp_send_message() should return zero on success and
cannot propagate number of bytes as returned by internally
called mei_cldev_send().

Fixes: ee5cb39348e6 ("mei: pxp: recover from recv fail under memory pressure")
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Link: https://lore.kernel.org/r/20231126092449.88310-1-tomas.winkler@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>