remoteproc: k3-r5: Drop check performed in k3_r5_rproc_{mbox_callback/kick}

remoteproc: k3-r5: Drop check performed in k3_r5_rproc_{mbox_callback/kick}

Commit f3f11cfe8907 ("remoteproc: k3-r5: Acquire mailbox handle during
probe routine") introduced a check in the "k3_r5_rproc_mbox_callback()"
and "k3_r5_rproc_kick()" callbacks, causing them to exit if the remote
core's state is "RPROC_DETACHED". However, the "__rproc_attach()"
function that is responsible for attaching to a remote core, updates
the state of the remote core to "RPROC_ATTACHED" only after invoking
"rproc_start_subdevices()".

The "rproc_start_subdevices()" function triggers the probe of the Virtio
RPMsg devices associated with the remote core, which require that the
"k3_r5_rproc_kick()" and "k3_r5_rproc_mbox_callback()" callbacks are
functional. Hence, drop the check in the callbacks.

Fixes: f3f11cfe8907 ("remoteproc: k3-r5: Acquire mailbox handle during probe routine")
Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Signed-off-by: Beleswar Padhi <b-padhi@ti.com>
Tested-by: Judith Mendez <jm@ti.com>
Reviewed-by: Andrew Davis <afd@ti.com>
Link: https://lore.kernel.org/r/20250513054510.3439842-2-b-padhi@ti.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>