samples: openamp_rsc_table: remove unused config

Remove the FW_READY reply config, as it's not required for
the M7 core on i.MX8M Plus.
This setting triggers an interrupt to the host, which is
unnecessary in the case of M7 (check host-side imx_rproc
driver in Linux).

Signed-off-by: Iuliana Prodan <iuliana.prodan@nxp.com>